Search

Your search keyword '"Chaves, Anderson"' showing total 181 results
Start Over Author "Chaves, Anderson" Publication Year Range Last 50 years
181 results on '"Chaves, Anderson"'

1. Computational prediction of high thermoelectric performance in As$_{2}$Se$_{3}$ by engineering out-of-equilibrium defects

Author

Chaves, Anderson S., Silva, Murilo Aguiar, and Antonelli, Alex

Subjects
Condensed Matter - Materials Science
Abstract

We employed first-principles calculations to investigate the thermoelectric transport properties of the compound As$_2$Se$_3$. Early experiments and calculations have indicated that these properties are controlled by a kind of native defect called antisites. Our calculations using the linearized Boltzmann transport equation within the relaxation time approximation show good agreement with the experiments for defect concentrations of the order of 10$^{19}$ cm$^{-3}$. Based on our total energy calculations, we estimated the equilibrium concentration of antisite defects to be about 10$^{14}$ cm$^{-3}$. These results suggest that the large concentration of defects in the experiments is due to kinetic and/or off-stoichiometry effects and in principle it could be lowered, yielding relaxation times similar to those found in other chalcogenide compounds. In this case, for relaxation time higher than 10 fs, we obtained high thermoelectric figures of merit of 3 for the p-type material and 2 for the n-type one., Comment: 8 pages, 5 figures, regular article

Published
2023

2. Semiclassical Electron and Phonon Transport from First Principles: Application to Layered Thermoelectrics

Author

Chaves, Anderson S., Pizzochero, Michele, Larson, Daniel T., Antonelli, Alex, and Kaxiras, Efthimios

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Thermoelectrics are a promising class of materials for renewable energy owing to their capability to generate electricity from waste heat, with their performance being governed by a competition between charge and thermal transport. A detailed understanding of energy transport at the nanoscale is thus of paramount importance for developing efficient thermoelectrics. Here, we provide a comprehensive overview of the methodologies adopted for the computational design and optimization of thermoelectric materials from first-principles calculations. First, we introduce density-functional theory, the fundamental tool to describe the electronic and vibrational properties of solids. Next, we review charge and thermal transport in the semiclassical framework of the Boltzmann transport equation, with a particular emphasis on the various scattering mechanisms between phonons, electrons, and impurities. Finally, we illustrate how these approaches can be deployed in determining the figure of merit of tin and germanium selenides, an emerging family of layered thermoelectrics that exhibits a promising figure of merit. Overall, this review article offers practical guidelines to achieve an accurate assessment of the thermoelectric properties of materials by means of computer simulations., Comment: 64 pages, 7 figures, revised version

Published
2023

3. Outstanding thermoelectric performance predicted for out-of-plane p-doped GeSe

Author

Chaves, Anderson S., Larson, Daniel T., Kaxiras, Efthimios, and Antonelli, Alex

Subjects
Condensed Matter - Materials Science
Abstract

The record-breaking thermoelectric performance of tin selenide (SnSe) has motivated the investigation of analogue compounds with the same structure. A promising candidate that emerged recently is germanium selenide (GeSe). Here, using extensive first-principles calculations of the hole-phonon and hole-impurity scattering, we investigate the thermoelectric transport properties of the orthorhombic phase of p-doped GeSe. We predict outstanding thermoelectric performance for GeSe over a broad range of temperatures due to its high Seebeck coefficients, extremely low Lorenz numbers, ultralow total thermal conductivity, and relatively large band gap. In particular, the out-of-plane direction in GeSe presents equivalent or even higher performance than SnSe for temperatures above 500 K. By extending the analysis to 900 K, we obtained an ultrahigh value for the thermoelectric figure of merit (zT = 3.2) at the optimal hole density of 4x10^19 cm^-3. Our work provides strong motivation for continued experimental work focusing on improving the GeSe doping efficiency in order to achieve this optimal hole density., Comment: 13 pages, 7 figures

Published
2022

5. Microscopic origin of the excellent thermoelectric performance in n-doped SnSe

Author

Chaves, Anderson S., Larson, Daniel T., Kaxiras, Efthimios, and Antonelli, Alex

Subjects
Condensed Matter - Materials Science
Abstract

Excellent thermoelectric performance in the out-of-layer n-doped SnSe has been observed experimentally (Chang et al., Science 360, 778-783 (2018)). However, a first-principles investigation of the dominant scattering mechanisms governing all thermoelectric transport properties is lacking. In the present work, by applying extensive first-principles calculations of electron-phonon coupling associated with the calculation of the scattering by ionized impurities, we investigate the reasons behind the superior figure of merit as well as the enhancement of zT above 600 K in n-doped out-of-layer SnSe, as compared to p-doped SnSe with similar carrier densities. For the n-doped case, the relaxation time is dominated by ionized impurity scattering and increases with temperature, a feature that maintains the power factor at high values at higher temperatures and simultaneously causes the carrier thermal conductivity at zero electric current (k_el) to decrease faster for higher temperatures, leading to an ultrahigh-zT = 3.1 at 807 K. We rationalize the roles played by k_el and k^0 (the thermal conductivity due to carrier transport under isoelectrochemical conditions) in the determination of zT. Our results show the ratio between k^0 and the lattice thermal conductivity indeed corresponds to the upper limit for zT, whereas the difference between calculated zT and the upper limit is proportional to k_el., Comment: 12 pages, 5 figures

Published
2021
Full Text
View/download PDF

7. Boosting the efficiency of ab initio electron-phonon coupling calculations through dual interpolation

Author

Chaves, Anderson S., Antonelli, Alex, Larson, Daniel T., and Kaxiras, Efthimios

Subjects
Condensed Matter - Materials Science, Physics - Computational Physics
Abstract

The coupling between electrons and phonons in solids plays a central role in describing many phenomena, including superconductivity and thermoelecric transport. Calculations of this coupling are exceedingly demanding as they necessitate integrations over both the electron and phonon momenta, both of which span the Brillouin zone of the crystal, independently. We present here an ab initio method for efficiently calculating electron-phonon mediated transport properties by dramatically accelerating the computation of the double integrals with a dual interpolation technique that combines maximally localized Wannier functions with symmetry-adapted plane waves. The performance gain in relation to the current state-of-the-art Wannier-Fourier interpolation is approximately 2n_s \times M, where n_s is the number of crystal symmetry operations and M, a number in the range 5 - 60, governs the expansion in star functions. We demonstrate with several examples how our method performs some ab initio calculations involving electron-phonon interactions., Comment: 9 pages, 5 figures

Published
2020
Full Text
View/download PDF

8. Investigating charge carrier scattering processes in anisotropic semiconductors through first-principles calculations: The case of p-type SnSe

Author

Chaves, Anderson S., González-Romero, Robert Luis, Meléndez, Juan J., and Antonelli, Alex

Subjects
Condensed Matter - Materials Science, Physics - Computational Physics
Abstract

Efficient ab initio computational methods for the calculation of thermoelectric transport properties of materials are of great avail for energy harvesting technologies. The BoltzTraP code has been largely used to efficiently calculate thermoelectric coefficients. However, its current version that is publicly available is based only on the constant relaxation time (RT) approximation, which usually does not hold for real materials. Here, we extended the implementation of the BoltzTraP code by incorporating realistic k-dependent RT models of the temperature dependence of the main scattering processes, namely, screened polar and nonpolar scattering by optical phonons, scattering by acoustic phonons, and scattering by ionized impurities with screening. Our RT models are based on a smooth Fourier interpolation of Kohn-Sham eigenvalues and its derivatives, taking into account non-parabolicity (beyond the parabolic or Kane models), degeneracy and multiplicity of the energy bands on the same footing, within very low computational cost. In order to test our methodology, we calculated the anisotropic thermoelectric transport properties of low temperature phase (Pnma) of intrinsic p-type and hole-doped tin selenide (SnSe). Our results are in quantitative agreement with experimental data, regarding the evolution of the anisotropic thermoelectric coefficients with both temperature and chemical potential. Hence, from this picture, we also obtained the evolution and understanding of the main scattering processes of the overall thermoelectric transport in p-type SnSe.

Published
2020
Full Text
View/download PDF

9. DJEnsemble: On the Selection of a Disjoint Ensemble of Deep Learning Black-Box Spatio-Temporal Models

Author

Souto, Yania Molina, Pereira, Rafael, Zorrilla, Rocío, Chaves, Anderson, Tsan, Brian, Rusu, Florin, Ogasawara, Eduardo, Ziviani, Artur, and Porto, Fabio

Subjects
Computer Science - Artificial Intelligence, Computer Science - Machine Learning
Abstract

In this paper, we present a cost-based approach for the automatic selection and allocation of a disjoint ensemble of black-box predictors to answer predictive spatio-temporal queries. Our approach is divided into two parts -- offline and online. During the offline part, we preprocess the predictive domain data -- transforming it into a regular grid -- and the black-box models -- computing their spatio-temporal learning function. In the online part, we compute a DJEnsemble plan which minimizes a multivariate cost function based on estimates for the prediction error and the execution cost -- producing a model spatial allocation matrix -- and run the optimal ensemble plan. We conduct a set of extensive experiments that evaluate the DJEnsemble approach and highlight its efficiency. We show that our cost model produces plans with performance close to the actual best plan. When compared against the traditional ensemble approach, DJEnsemble achieves up to $4X$ improvement in execution time and almost $9X$ improvement in prediction accuracy. To the best of our knowledge, this is the first work to solve the problem of optimizing the allocation of black-box models to answer predictive spatio-temporal queries.

Published
2020

10. CALANGO: A phylogeny-aware comparative genomics tool for discovering quantitative genotype-phenotype associations across species

Author

Hongo, Jorge Augusto, de Castro, Giovanni Marques, Albuquerque Menezes, Alison Pelri, Rios Picorelli, Agnello César, Martins da Silva, Thieres Tayroni, Imada, Eddie Luidy, Marchionni, Luigi, Del-Bem, Luiz-Eduardo, Vieira Chaves, Anderson, Almeida, Gabriel Magno de Freitas, Campelo, Felipe, and Lobo, Francisco Pereira

Published
2023
Full Text
View/download PDF

11. Chemical modification of clay nanocomposites for the improvement of the catalytic properties of Lipase A from Candida antarctica

Author

Cavalcante, Antônio Luthierre Gama, Chaves, Anderson Valério, Fechine, Pierre Basílio Almeida, Holanda Alexandre, Jeferson Yves Nunes, Freire, Tiago Melo, Davi, Dalila Maria Barbosa, Neto, Francisco Simão, de Sousa, Isamayra Germano, da Silva Moreira, Katerine, de Oliveira, André Luiz Barros, de Mattos, Marcos Carlos, Oliveira, Maria Conceição Ferreira, de Brito, Maria Vieira, Ballereau, Stéphanie, Bernardes-Génisson, Vania, da Fonseca, Aluísio Marques, and dos Santos, José C.S.

Published
2022
Full Text
View/download PDF

12. Ultralow and Anisotropic Thermal Conductivity in Semiconductor As2Se3

Author

González-Romero, Robert L., Antonelli, Alex, Chaves, Anderson S., and Meléndez, Juan J.

Subjects
Condensed Matter - Materials Science
Abstract

An ultralow lattice thermal conductivity of 0.14 W$\cdot$ m$^{-1} \cdot$ K$^{-1}$ along the $\vec b$ axis of As$_2$Se$_3$ single crystals was obtained at 300 K by first-principles calculations involving the density functional theory and the resolution of the Boltzmann transport equation. This ultralow lattice thermal conductivity arises from the combination of two mechanisms: 1) a cascade-like fall of the low-lying optical modes, which results in avoided crossings of these with the acoustic modes, low sound velocities and increased scattering rates of the acoustic phonons; and 2) the repulsion between the lone-pair electrons of the As cations and the valence $p$ orbitals of the Se anions, which leads to an increase in the anharmonicity of the bonds. The physical origins of these mechanisms lie on the nature of the chemical bonding in the material and its strong anisotropy. These results, whose validity has been addressed by comparison with SnSe, for which excellent agreement between the theoretical predictions and the experiments is achieved, point out that As$_2$Se$_3$ could exhibit improved thermoelectric properties.

Published
2017
Full Text
View/download PDF

13. Taguchi design-assisted co-immobilization of lipase A and B from Candida antarctica onto chitosan: Characterization, kinetic resolution application, and docking studies

Author

da S. Moreira, Katerine, Barros de Oliveira, André Luiz, Saraiva de Moura Júnior, Lourembergue, Germano de Sousa, Isamayra, Luthierre Gama Cavalcante, Antonio, Simão Neto, Francisco, Bussons Rodrigues Valério, Roberta, Valério Chaves, Anderson, de Sousa Fonseca, Thiago, Morais Vieira Cruz, Daniel, Vieira Lima, Gledson, de Oliveira, Gabriel Paixão, de Souza, Maria Cristiane Martins, Basílio Almeida Fechine, Pierre, de Mattos, Marcos Carlos, Marques da Fonseca, Aluísio, and dos Santos, José C.S.

Published
2022
Full Text
View/download PDF

17. A novel hybrid biocatalyst from immobilized Eversa® Transform 2.0 lipase and its application in biolubricant synthesis.

Author

Germano de Sousa, Isamayra, Valério Chaves, Anderson, de Oliveira, André Luiz Barros, da Silva Moreira, Katerine, Gonçalves de Sousa Junior, Paulo, Simão Neto, Francisco, Cristina Freitas de Carvalho, Simone, Bussons Rodrigues Valério, Roberta, Vieira Lima, Gledson, Sanders Lopes, Ada Amélia, Martins de Souza, Maria Cristiane, da Fonseca, Aluísio Marques, Fechine, Pierre Basílio Almeida, de Mattos, Marcos Carlos, and dos Santos, José C. S.

Subjects
*LIPASES, *GLUTARALDEHYDE, *ENZYMES, *FOURIER transform infrared spectroscopy, *ORGANIC solvents, *IONIC strength
Abstract

In this study, a Taguchi experimental design was used for optimzing the immobilization of the lipase Eversa® Transform 2.0 (EVS) onto a hybrid support consisting of chitosan (CHI) and agarose (AGA), with glutaraldehyde (GLU) used as the support activator. The biocatalyst obtained was characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TGA), Energy Dispersive Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). The optimized reaction conditions (60 min, 5 mM ionic strength, 1% GLU concentration, and 5 mg protein load per g of support) resulted in a highly active biocatalyst (74.39 ± 0.48 U/g) and delivered an immobilization yield of 74.20 ± 0.28%. The biocatalyst produced was observed to lose only 15.3% of its activity after 61 days of storage. The activity was also observed to increase by 96.70% ± 0.76, 27.34% ± 2.34, and 84.35% ± 1.68 in the presence of the organic solvents hexane, cyclohexane, and methanol, respectively. Additionally, the byocatalist showed more pronounced activity at temperatures above 50 °C and was still able to retain approximately 30% of it at 70 °C. These values were found to be higher at alkaline pHs, as the activity of Eversa® 2.0 Transform saw an increase of up to 140% at pH 9. The desorption tests performed did not reveal any enzymatic detachment from the support. The novel biocatalyst also showed promising ester-lubricating properties. Furthermore, the in silico study revealed a binding affinity of −5.1 kcal/mol between oleic acid and the enzyme, suggesting that the combination of the substrate and the lipase was more stable and therefore, suitable for esterification. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

18. Computational prediction of high thermoelectric performance in As2Se3 by engineering out-of-equilibrium defects.

Author

Chaves, Anderson Silva, Silva, Murilo Aguiar, and Antonelli, Alex

Abstract

We employed first-principles calculations to investigate the thermoelectric transport properties of the compound As2Se3. Early experiments and calculations have indicated that these properties are controlled by a kind of native defect called antisites. Our calculations using the linearized Boltzmann transport equation within the relaxation time approximation show good agreement with the experiments for defect concentrations of the order of 1019 cm−3. Based on our total energy calculations, we estimated the equilibrium concentration of antisite defects to be about 1014 cm−3. These results suggest that the large concentration of defects in the experiments is due to kinetic and/or off-stoichiometry effects and in principle it could be lowered, yielding relaxation times similar to those found in other chalcogenide compounds. In this case, for relaxation time higher than 10 fs, we obtained high thermoelectric figures of merit of 3 for the p-type material and 2 for the n-type one. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

22. Does the Size of Nanohydroxyapatite Associated With Anionic Collagen Scaffolds Interferes With Osteoblasts Bioactivity?

Author

Freire, Gildênio Estavam, primary, Carvalho, Elayne Valério, additional, Veras, Mariana de Oliveira Viana, additional, Costa, Deiziane Viana Silva, additional, Rebouças, Conceição da Silva Martins, additional, Silva, Guilherme Ferreira Maciel, additional, Morais, Maria Luana Gaudencio dos Santos, additional, Góes, Paula, additional, Chaves, Anderson Valério, additional, Fechine, Pierre Basílio Almeida, additional, Brito, Gerly Anne de Castro, additional, Ferreira, Júlio César Góes, additional, and Leitão, Renata Ferreira de Carvalho, additional

Published
2023
Full Text
View/download PDF

23. A novel hybrid biocatalyst from immobilized Eversa® Transform 2.0 lipase and its application in biolubricant synthesis

Author

Germano de Sousa, Isamayra, primary, Valério Chaves, Anderson, additional, de Oliveira, André Luiz Barros, additional, da Silva Moreira, Katerine, additional, Gonçalves de Sousa Junior, Paulo, additional, Simão Neto, Francisco, additional, Cristina Freitas de Carvalho, Simone, additional, Bussons Rodrigues Valério, Roberta, additional, Vieira Lima, Gledson, additional, Sanders Lopes, Ada Amélia, additional, Martins de Souza, Maria Cristiane, additional, da Fonseca, Aluísio Marques, additional, Fechine, Pierre Basílio Almeida, additional, de Mattos, Marcos Carlos, additional, and dos Santos, José C. S., additional

Published
2022
Full Text
View/download PDF

24. Chitosan-Based Nanoparticles for Cardanol-Sustained Delivery System

Author

Valério, Roberta Bussons Rodrigues, primary, da Silva, Nilvan Alves, additional, Junior, José Ribamar Paiva, additional, Chaves, Anderson Valério, additional, de Oliveira, Bruno Peixoto, additional, Souza, Nágila Freitas, additional, de Morais, Selene Maia, additional, Santos, José Cleiton Sousa dos, additional, and Abreu, Flávia Oliveira Monteiro da Silva, additional

Published
2022
Full Text
View/download PDF

28. MEMORIAS DEL V CONGRESO INTERNACIONAL DE INVESTIGACIÓN EN EDUCACIÓN, EMPRESA Y SOCIEDAD CIDIEES 2022

Author

Cuevas, Manuel Fernando González, Granados, John Mauricio Sandoval, ANA MARIA GAYOL GONZÁLEZ, Dávalos, Raúl Marcelo Ferrer, Reyes, Erika María Roncancio, Medina, José Eriberto Cifuentes, Romero, Juan Carlos Rangel, Rivas, Maria Paula Losada, Suly Viviana Delgado Fierro, Gonzalez, Brayan Davis Bohorquez, Rico, Jesús Alberto Morales, Golondrino, Gabriel Elías Chanchí, Echeverry, Juan José, Quintero, Jairo Andrés Meneses, Romero, Angelica Hernandez, Caicedo, Adrian Marcel Garcia, Medina, Jorge Enrique Chaparro, Rodríguez, Isabel Cristina Rincón, Serrano, Diego Leonardo Cruz, Rodríguez, Martha Liliana Rincón, Sánchez, José Gregorio Noroño, Beltrán, Nelson Hernando Gómez, Johimer Andrés Gasca Peña, Hernández, Angel Enrique Hernández, Reyes, Tatiana Hernández, Rosales, Verónica Miranda, Moyano, Wendy Patricia Beltran, Vargas, Yesica Maria Ardila, Wilches, Luz Adriana Peña, Camperos, Yadira Del Pilar, NANCY PATRICIA CAVIEDES CASTILLO, RAUL FRANCISCO MATEUS TOVAR, Briyith Paola Chajín Salcedo, Rivera, Carlos Vergara, Mejía, Marcela Poveda, Diaz, Lina Duque, Paez, Rosalba, Pacheco, Nancy Patricia García, Orduz, Ángela María Rodríguez, Cardona, Luís Fernando Botero, Myrian Celeste Benítez González, Stefany Carrillo García, Carrión, Flor Noemi Celi, Raza, Edison Fabian Miranda, Arévalo, Diego Fernando Pineda, Suárez, Carlos Nelson Cobos, Rangel, Mónica Andrea Guío, Muñoz, Carlos Alfonso Toquica, Ariza, Angela María Vargas, Forero, Janeth Cecilia Gil, Quintero, Alejandra López, Gonzales, Nicolás Gomez, Quiñonez, Liliana Ayala, Natra Patricia Benavides Torres, Márquez, Jose Alonso Caballero, Rodríguez, Paola Andrea Pabón, Pérez, Mauricio José Martínez, Pelagio, Ricardo Cristhian Morales, Mercado, Juan Manuel Castro, Jiménez, Diego Silva, Mayorga, Alexis Valenzuela, Guzmán, Gonzalo Soto, VICTORIA EUGENIA PINO TERÁN, JULIAN ENRIQUE BARRERO GARCIA, DAGOBERTO ALEXIS MACHADO SANCHEZ, De López, Luciana Dalila Coronel, Ortiz, Diana Catalina Santamaria, Nova, Omar Hernan, Baldevenites, Elisabeth Viviana Lucero, Sánchez, Claudia Patricia Rivera, Giraldo Arcila Fabio Nelson, Gasca, Leidy Johanna Osorio, Sarmiento, Daniel Márquez, Chrystian Mauricio Pérez Serna, Molina, Juan Camilo Murillo, Limón, Florentino Rocha, Castillo, Frank Sebastian Naranjo, Riveros, Ana Sofia Lopera, Rodriguez, Francisco Alfonso Lanza, Sánchez, Edgar Ezequiel Luna, Tapias, Irving Herney Pinzón, Arcila, Fabio Nelson Giraldo, Varela, Valentina Blandón, García, Daniela García, Dayaris Jheliksa Ropero Casiano, Díaz, Luisa María Sánchez, Quiceno, Cristian Camilo Ramírez, Urrutia, Jorge Alberto Vidal, Muñoz, Germán Oliver Sanhueza, González, Laura Elizabeth Cavazos, Cuellar, Erika Alejandra Yepez, Estelvina Rodríguez Portillo, Duré, Jorge Alberto Alonso, Bernal, Carolina Arguello, Moscoso, Jose Limón, Ipia, Paula Camila Vanegas, Katherin Jineth Rodríguez Calderón, Mesa, Daniela Estrada, Montealegre, Javier Darío, Pedraza, Ivone Karina Tejada, Cesar-Halley Limaymanta-Álvarez, Apaza-Tapia, Ludgarda, Yábar, Silvia Verónica Valdivia, Orduz, Rolando Fabián Junco, Machuca, Henry Mauricio Rojas, Díaz, Nathalia Andrea Cuervo, Castañeda, Cristian Camilo Cuevas, De Lourdes Ahumada Ruíz, María, ANDREA CAROLINA RODRIGUEZ FERNÁNDEZ, Vargas, Pablo Esteban Arias, Calderón, Julie Carolina Armenta, Chavez, María Fernanda Buitrago, Chaves, Anderson Iván González, Vega, Asdrúbal Henao, Sierra, Andrés Julián Guzmán, YANNINA MITZA ARIAS HUACO, Valdivia, Gabriela Cornejo, Luza, Carolina Kennedy Salas, Pedraza, Luisa Tatiana Tejada, Cruz, José Daniel Cabrera, Montoya, Guadalupe Nieto, Zárate, Estela Araceli Mora, Vázquez, Cinthia Hernández, Ortegón, Mónica Viviana Vargas, Lara, Tania Lizveth Orjuela, Parada, Wilson Giovanny León, Díaz, Omar Joel Benites, JHON FREDDY VEGA DUARTE, Vargas, Mónica Yadira Ángel, Nelsy Yolanda Bautista Garavito, Niño, Karen Daza, Mendoza, Rossana Ninoska Camelo, Deiner Javier Andrade Mora, Zuleta, Carlos Arturo Riveira, Romero, Claudia Maria Valdés, Gutiérrez, Cristian Jaccob Obando, Salcedo, Guillermo Meza, González, Sandra Marcela Espitia, Garcia, Paula Gissela Uribe, HINCAPIE OSORIO LAURA ALEJANDRA, Rodriguez, Diana Beatriz Chavarría, Oviedo, Paula Camila Martin, and Ttito, Yonathan Mario Gonzales

Published
2022
Full Text
View/download PDF

29. LA INVESTIGACIÓN CIENTÍFICA NUEVAS REALIDADES

Author

Ttito, Yonathan Mario Gonzales, Márquez, Jose Alonso Caballero, Rodríguez, Paola Andrea Pabón, Pérez, Mauricio José Martínez, Pelagio, Ricardo Cristhian Morales, Chrystian Mauricio Pérez Serna, Molina, Juan Camilo Murillo, Moyano, Wendy Patricia Beltran, Vargas, Yesica Maria Ardila, Beltrán, Nelson Hernando Gómez, Johimer Andrés Gasca Peña, Pedraza, Luisa Tatiana Tejada, Cruz, José Daniel Cabrera, Ortegón, Mónica Viviana Vargas, Lara, Tania Lizveth Orjuela, Mesa, Daniela Estrada, Montealegre, Javier Darío, Gutiérrez, Cristian Jaccob Obando, Salcedo, Guillermo Meza, Romero, Angelica Hernandez, Caicedo, Adrian Marcel Garcia, Mercado, Juan Manuel Castro, Díaz, Omar Joel Benites, YANNINA MITZA ARIAS HUACO, Valdivia, Gabriela Cornejo, Luza, Carolina Kennedy Salas, Carrión, Flor Noemi Celi, Raza, Edison Fabian Miranda, Arévalo, Diego Fernando Pineda, Suárez, Carlos Nelson Cobos, González, Laura Elizabeth Cavazos, Katherin Jineth Rodríguez Calderón, Rivas, Maria Paula Losada, Suly Viviana Delgado Fierro, Cuevas, Manuel Fernando González, Granados, John Mauricio Sandoval, De Lourdes Ahumada Ruíz, María, Quintero, Jairo Andrés Meneses, Zárate, Estela Araceli Mora, Muñoz, Germán Oliver Sanhueza, Limón, Florentino Rocha, Vázquez, Cinthia Hernández, Calderón, Julie Carolina Armenta, Medina, Jorge Enrique Chaparro, Rodríguez, Isabel Cristina Rincón, Serrano, Diego Leonardo Cruz, Rodríguez, Martha Liliana Rincón, Sánchez, José Gregorio Noroño, Natra Patricia Benavides Torres, NANCY PATRICIA CAVIEDES CASTILLO, RAUL FRANCISCO MATEUS TOVAR, Myrian Celeste Benítez González, JULIAN ENRIQUE BARRERO GARCIA, DAGOBERTO ALEXIS MACHADO SANCHEZ, Tapias, Irving Herney Pinzón, Mejía, Marcela Poveda, Diaz, Lina Duque, Paez, Rosalba, Hernández, Angel Enrique Hernández, Reyes, Tatiana Hernández, Rosales, Verónica Miranda, Cuellar, Erika Alejandra Yepez, Baldevenites, Elisabeth Viviana Lucero, Sánchez, Edgar Ezequiel Luna, González, Ana María Gayol, Arcila, Fabio Nelson Giraldo, Sánchez, Claudia Patricia Rivera, Dayaris Jheliksa Ropero Casiano, Díaz, Luisa María Sánchez, Quiceno, Cristian Camilo Ramírez, JHON FREDDY VEGA DUARTE, SANDRA MARCELA ESPITIA GONZALEZ, ANA MARIA GAYOL GONZÁLEZ, Pacheco, Nancy Patricia García, Orduz, Ángela María Rodríguez, Cardona, Luís Fernando Botero, De López, Luciana Dalila Coronel, Mayorga, Alexis Valenzuela, Jiménez, Diego Silva, Rangel, Mónica Andrea Guío, Chavez, María Fernanda Buitrago, Chaves, Anderson Iván González, Vega, Asdrúbal Henao, Oviedo, Paula Camila Martin, Moscoso, Jose Limón, Parada, Wilson Giovanny León, Cesar-Halley Limaymanta-Álvarez, Apaza-Tapia, Ludgarda, Yábar, Silvia Verónica Valdivia, Ortiz, Diana Catalina Santamaria, Gonzalez, Sandra Marcela Espitia, Nova, Omar Hernan, Reyes, Erika María Roncancio, Medina, José Eriberto Cifuentes, Mendoza, Rossana Ninoska Camelo, Deiner Javier Andrade Mora, Zuleta, Carlos Arturo Riveira, Romero, Claudia Maria Valdés, Urrutia, Jorge Alberto Vidal, Romero, Juan Carlos Rangel, Pedraza, Ivone Karina Tejada, Castillo, Frank Sebastian Naranjo, Riveros, Ana Sofia Lopera, and Rodriguez, Francisco Alfonso Lanza

Published
2022
Full Text
View/download PDF

30. Libro de actas: La Investigación Científica Transdisciplinaria Tomo III

Author

Cuevas, Manuel Fernando González, Granados, John Mauricio Sandoval, ANA MARIA GAYOL GONZÁLEZ, Dávalos, Raúl Marcelo Ferrer, Reyes, Erika María Roncancio, Medina, José Eriberto Cifuentes, Romero, Juan Carlos Rangel, Rivas, Maria Paula Losada, Suly Viviana Delgado Fierro, Gonzalez, Brayan Davis Bohorquez, Rico, Jesús Alberto Morales, Golondrino, Gabriel Elías Chanchí, Echeverry, Juan José, Quintero, Jairo Andrés Meneses, Romero, Angelica Hernandez, Caicedo, Adrian Marcel Garcia, Medina, Jorge Enrique Chaparro, Rodríguez, Isabel Cristina Rincón, Serrano, Diego Leonardo Cruz, Rodríguez, Martha Liliana Rincón, Sánchez, José Gregorio Noroño, Beltrán, Nelson Hernando Gómez, Johimer Andrés Gasca Peña, Hernández, Angel Enrique Hernández, Reyes, Tatiana Hernández, Rosales, Verónica Miranda, Moyano, Wendy Patricia Beltran, Vargas, Yesica Maria Ardila, Wilches, Luz Adriana Peña, Camperos, Yadira Del Pilar, NANCY PATRICIA CAVIEDES CASTILLO, RAUL FRANCISCO MATEUS TOVAR, Briyith Paola Chajín Salcedo, Rivera, Carlos Vergara, Mejía, Marcela Poveda, Diaz, Lina Duque, Paez, Rosalba, Pacheco, Nancy Patricia García, Orduz, Ángela María Rodríguez, Cardona, Luís Fernando Botero, Myrian Celeste Benítez González, Stefany Carrillo García, Carrión, Flor Noemi Celi, Raza, Edison Fabian Miranda, Arévalo, Diego Fernando Pineda, Suárez, Carlos Nelson Cobos, Rangel, Mónica Andrea Guío, Muñoz, Carlos Alfonso Toquica, Ariza, Angela María Vargas, Forero, Janeth Cecilia Gil, Quintero, Alejandra López, Gonzales, Nicolás Gomez, Quiñonez, Liliana Ayala, Natra Patricia Benavides Torres, Márquez, Jose Alonso Caballero, Rodríguez, Paola Andrea Pabón, Pérez, Mauricio José Martínez, Pelagio, Ricardo Cristhian Morales, Mercado, Juan Manuel Castro, Jiménez, Diego Silva, Mayorga, Alexis Valenzuela, Guzmán, Gonzalo Soto, VICTORIA EUGENIA PINO TERÁN, JULIAN ENRIQUE BARRERO GARCIA, DAGOBERTO ALEXIS MACHADO SANCHEZ, De López, Luciana Dalila Coronel, Ortiz, Diana Catalina Santamaria, Gonzalez, Sandra Marcela Espitia, Nova, Omar Hernan, González, Ana María Gayol, Baldevenites, Elisabeth Viviana Lucero, Sánchez, Claudia Patricia Rivera, Giraldo Arcila Fabio Nelson, Gasca, Leidy Johanna Osorio, Sarmiento, Daniel Márquez, Chrystian Mauricio Pérez Serna, Molina, Juan Camilo Murillo, Limón, Florentino Rocha, Castillo, Frank Sebastian Naranjo, Riveros, Ana Sofia Lopera, Rodriguez, Francisco Alfonso Lanza, Sánchez, Edgar Ezequiel Luna, Tapias, Irving Herney Pinzón, Arcila, Fabio Nelson Giraldo, Varela, Valentina Blandón, García, Daniela García, Dayaris Jheliksa Ropero Casiano, Díaz, Luisa María Sánchez, Quiceno, Cristian Camilo Ramírez, Urrutia, Jorge Alberto Vidal, Muñoz, Germán Oliver Sanhueza, González, Laura Elizabeth Cavazos, Cuellar, Erika Alejandra Yepez, Estelvina Rodríguez Portillo, Duré, Jorge Alberto Alonso, Bernal, Carolina Arguello, Moscoso, Jose Limón, Ipia, Paula Camila Vanegas, Katherin Jineth Rodríguez Calderón, Mesa, Daniela Estrada, Montealegre, Javier Darío, Pedraza, Ivone Karina Tejada, Cesar-Halley Limaymanta-Álvarez, Apaza-Tapia, Ludgarda, Yábar, Silvia Verónica Valdivia, Orduz, Rolando Fabián Junco, Machuca, Henry Mauricio Rojas, Díaz, Nathalia Andrea Cuervo, Castañeda, Cristian Camilo Cuevas, De Lourdes Ahumada Ruíz, María, ANDREA CAROLINA RODRIGUEZ FERNÁNDEZ, Vargas, Pablo Esteban Arias, Calderón, Julie Carolina Armenta, Chavez, María Fernanda Buitrago, Chaves, Anderson Iván González, Vega, Asdrúbal Henao, Sierra, Andrés Julián Guzmán, YANNINA MITZA ARIAS HUACO, Valdivia, Gabriela Cornejo, Luza, Carolina Kennedy Salas, Pedraza, Luisa Tatiana Tejada, Cruz, José Daniel Cabrera, Montoya, Guadalupe Nieto, Zárate, Estela Araceli Mora, Vázquez, Cinthia Hernández, Ortegón, Mónica Viviana Vargas, Lara, Tania Lizveth Orjuela, Parada, Wilson Giovanny León, Díaz, Omar Joel Benites, JHON FREDDY VEGA DUARTE, Vargas, Mónica Yadira Ángel, Nelsy Yolanda Bautista Garavito, Niño, Karen Daza, Mendoza, Rossana Ninoska Camelo, Deiner Javier Andrade Mora, Zuleta, Carlos Arturo Riveira, Romero, Claudia Maria Valdés, Gutiérrez, Cristian Jaccob Obando, Salcedo, Guillermo Meza, Garcia, Paula Gissela Uribe, HINCAPIE OSORIO LAURA ALEJANDRA, Rodriguez, Diana Beatriz Chavarría, Oviedo, Paula Camila Martin, and Ttito, Yonathan Mario Gonzales

Published
2022
Full Text
View/download PDF

31. Out-of-plane thermoelectric performance for p-doped GeSe

Author

Chaves, Anderson Silva, 1986, Antonelli, Alex, 1954, and UNIVERSIDADE ESTADUAL DE CAMPINAS

Subjects
Fônons, Condutividade térmica, Thermal conductivity, Phonons, Artigo original, Thermoelectricity, Termoeletricidade
Abstract

Agradecimentos: A.S.C. and A.A. gratefully acknowledge support from the Brazilian agencies CNPq and FAPESP under Grants No. 2010/16970-0, No. 2013/08293-7, No. 2015/26434-2, No. 2016/23891-6, No. 2017/26105-4, and No. 2019/26088-8. D.T.L. acknowledges funding from the STC Center for Integrated Quantum Materials, NSF Grant No. DMR-1231319; NSF DMREF Award No. 1922172; and the Army Research Office under Cooperative Agreement No. W911NF-21-2-0147. The calculations were performed at CCJDR-IFGW-UNICAMP in Brazil Abstract: The record-breaking thermoelectric performance of tin selenide (SnSe) has motivated the investigation of analog compounds with the same structure. A promising candidate that emerged recently is germanium selenide (GeSe). Here, using extensive first-principles calculations of the hole-phonon and hole-impurity scattering, we investigate the thermoelectric transport properties of the orthorhombic phase of p-doped GeSe. We predict outstanding thermoelectric performance for GeSe over a broad range of temperatures due to its high Seebeck coefficients, extremely low Lorenz numbers, ultralow total thermal conductivity, and relatively large band gap. In particular, the out-of-plane direction in GeSe presents equivalent or even higher performance than SnSe for temperatures above 500 K. By extending the analysis to 900 K, we obtained an ultrahigh value for the thermoelectric figure of merit (zT = 3.2) at the optimal hole density of 4 x 10(19) cm(3). Our work provides strong motivation for continued experimental work focusing on improving the GeSe doping efficiency in order to achieve this optimal hole density CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Published
2022

33. CALANGO: a phylogeny-aware comparative genomics tool for discovering quantitative genotype-phenotype associations across species

Author

Hongo, Jorge Augusto, primary, de Castro, Giovanni Marques, additional, Albuquerque Menezes, Alison Pelri, additional, Rios Picorelli, Agnello César, additional, da Silva, Thieres Tayroni Martins, additional, Imada, Eddie Luidy, additional, Marchionni, Luigi, additional, Del-Bem, Luiz-Eduardo, additional, Chaves, Anderson Vieira, additional, de Freitas Almeida, Gabriel Magno, additional, Campelo, Felipe, additional, and Lobo, Francisco Pereira, additional

Published
2021
Full Text
View/download PDF

35. Análise dos níveis de atividade física e índice de massa corporal de estudantes universitários: uma revisão sistemática

Author

Cardoso, Milena Oliveira, Chaves, Anderson Melo, Abreu, Pâmella Reis de, Silva, Allan Ruan Costa, Santos, Carla Letícia Borges dos, Maneschy, Mariela de Santana, Lima, Bráulio Nascimento, Júnior, Guanis de Barros Vilela, Novo, André, and Almeida, Klebson da Silva

Subjects
Índice de massa corporal, Aluno, Nível de atividade física, Saúde, Estilo de vida
Abstract

A qualidade de vida dos estudantes é diretamente afetada ao ingressar no ambiente acadêmico, devido à negligência aos cuidados a saúde, predispondo riscos como a obesidade. Desta forma, o objetivo principal do presente estudo foi identificar na literatura, artigos científicos, relacionados à qualidade de vida dos acadêmicos com o intuito de verificar e analisar os níveis de atividade física e o índice de massa corporal dos universitários. Os artigos foram selecionados nas seguintes bases de dados: PubMed, Scielo, ScienceDirect, Biblioteca virtual em saúde (BVS) e Cochrane. As três estratégias de buscas incluíram os descritores nos idiomas inglês e português: “estudantes universitários”, “acadêmicos” “índice de massa corporal”, “nível de atividade física” e “qualidade de vida”. A busca permitiu encontrar 16 artigos relacionados ao tema, nos quais se aplicou os critérios de inclusão e exclusão, resultando em 10 artigos, servindo de base para a elaboração desta revisão sistemática, o percurso de seleção dos artigos foram inseridos no fluxograma Prisma, em que os artigos selecionados após as fases de triagem e seleção, foram extraídos um total de nove parâmetros para serem reportados, incluindo autor, ano de publicação, título, objetivos, características da amostra, métodos adotados, testes/instrumentos utilizados, resultados obtidos e principais conclusões de cada estudo, distribuídos em três tabelas. Após resultados obtidos por meio dos métodos utilizados nas pesquisas, observou-se que os universitários, apresentaram um bom nível de atividade física e índice de massa corporal adequado, divergindo de estudos antigos nos quais o nível de sedentarismo e sobrepeso foi relativamente alto. A partir dos estudos realizados conclui-se que atualmente os estudantes universitários estão dentro do peso normal e ativo fisicamente diferente de estudos anteriores. É importante ressaltar que este estudo de revisão teve algumas limitações em sua construção, como a escassez de artigos sobre o tema desenvolvido e nos poucos selecionados observa-se uma não padronização de testes para verificação do nível de atividade física. info:eu-repo/semantics/publishedVersion

Published
2021

36. Investigating charge carrier scattering processes in anisotropic semiconductors through first-principles calculations : the case of p-type SnSe

Author

Chaves, Anderson Silva, 1986, Antonelli, Alex, 1954, and UNIVERSIDADE ESTADUAL DE CAMPINAS

Subjects
Cristais, Artigo original, Elétrons, Electrons, Ab initio calculations, Cálculos ab initio, Interpolação, Crystals, Interpolation
Abstract

Agradecimentos: ASC and AA gratefully acknowledge support from the Brazilian agencies CNPq and FAPESP under Grants #2010/16970-0, #2013/08293-7, #2015/26434-2, #2016/23891-6, #2017/26105-4, and #2019/26088-8. JJM acknowledges funding by the Ministerio de Economía y Competitividad, Agencia Estatal de Investigación, and Fondo Europeo de Desarrollo Regional (FEDER) (Spain and European Union) through Grant No. PGC2018-094763-B-I00, and by Junta de Extremadura (Spain) through Grant No. IB16013 (partially funded by FEDER). The calculations were performed at CCJDR-IFGW-UNICAMP in Brazil Abstract: Efficient ab initio computational methods for the calculation of the thermoelectric transport properties of materials are of great interest for energy harvesting technologies. The constant relaxation time approximation (CRTA) has been largely used to efficiently calculate thermoelectric coefficients. However, CRTA usually does not hold for real materials. Here we go beyond the CRTA by incorporating realistic k-dependent relaxation time models of the temperature dependence of the main scattering processes, namely, screened polar and nonpolar scattering by optical phonons, scattering by acoustic phonons, and scattering by ionized impurities with screening. Our relaxation time models are based on a smooth Fourier interpolation of Kohn-Sham eigenvalues and its derivatives, taking into account non-parabolicity (beyond the parabolic or Kane models), degeneracy and multiplicity of the energy bands on the same footing, within very low computational cost. In order to test our methodology, we calculated the anisotropic thermoelectric transport properties of the low temperature phase (Pnma) of intrinsic p-type and hole-doped tin selenide (SnSe). Our results are in quantitative agreement with experimental data, regarding the evolution of the anisotropic thermoelectric coefficients with both temperature and chemical potential. Hence, from this picture, we also obtained the evolution and understanding of the main scattering processes of the overall thermoelectric transport in p-type SnSe CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Published
2021

39. A experi?ncia de narrar o desconhecido: o engenho da fic??o no romance ?O irm?o alem?o?, de Chico Buarque

Author

Chaves, Anderson Trindade and Moreira, Maria Eunice

Subjects
Autofic??o, Self-fiction, Literatura brasileira, Chico Buarque, Brazilian literature, Romance, LETRAS [LINGUISTICA, LETRAS E ARTES]
Abstract

O presente trabalho tem por objetivo apresentar uma leitura de abordagem cr?tica do romance O irm?o alem?o, de Chico Buarque, de modo a analis?-lo enquanto composi??o narrativa que articula uma forma representa??o liter?ria amb?gua entre os seus referentes mim?ticos de uma realidade hist?rico-social e os seus ?ndices de ficcionaliza??o desse mesmo real a partir do relato de procura do narrador-protagonista por seu suposto irm?o judeu desaparecido no contexto de uma Alemanha nazista. Nesse sentido, fundamentamos nossa abordagem n?o somente nas formula??es te?ricas que d?o conta das assim chamadas ?narrativas do eu?, mas sobretudo nas que explicam a tradi??o do g?nero romance a partir de sua condi??o de ambiguidade frente ao mundo hist?rico-social do qual procede e participa, sobretudo, questionando-o e reinventando-o atrav?s de seus processo ficcionais. A partir disso, passamos ? an?lise propriamente dita do romance em quest?o, de modo a destacar a modula??o cambiante na estrutura de seus sentidos, o que impede que a obra seja apreciada por meio de um ?nico modelo de conven??o de escrita liter?ria. ? justamente a rela??o tensionada entre os seus estratos de significa??o que permitem n?veis de interpreta??o e leitura para a decodifica??o do romance. Assim, entendemos que o universo dos fatos narrados n?o resulta o mais importante na articula??o discursiva da obra. Pelo contr?rio, a experi?ncia de interpreta??o, percep??o sens?vel e imagina??o da realidade hist?rica pela perspectiva de um narrador-protagonista ? o que potencializa a express?o sem?ntica e ficcional da narrativa presente em O irm?o alem?o, de Chico Buarque. The present work aims to present a critical reading of novel O irm?o alem?o by Chico Buarque, in order to analyze it as a narrative composition that articulates an ambiguous literaty representation between its mimetic referents of a historical-social reality and their fictionalization indexes of that same reality from the narrador-protagonist?s account of the search for his supposed Jewish brother who disappeared in the context of a Nazi Germany. In this sense, we base our approach not only on the treoretical formulations that deal with the socalled ?narratives of the self?, but above all to those that explain the tradition of the novel/romance genre from its condition of ambiguity regarding historical-social world from which it comes and participates in and, above all, by questioning it and reinventing it through it fictional processes. From this, we move on to the proper analysis of the novel in question, in order to highlight the changing modulation in the structure of its meanings, which prevents the work from being appreciated through a single model of literary writing. It is precisely the strained relationship between its strata of meaning that allows levels of interpretation and reading for the decoding of the novel. Thus, we understand that the universe of the narrated facts is the most important in the discursive articulation of the narrative. On the contrary, the experience oh interpretation, sensitive perception and imagination of historical reality from the perspective of a narrator-protagonist is what plurify the semantic and fictional expression of the narrative present in O irm?o alem?o, by Chico Buarque.

Published
2020

40. Boosting the efficiency of ab initio electron-phonon coupling calculations through dual interpolation

Author

Chaves, Anderson Silva, 1986, Antonelli, Alex, 1954, and UNIVERSIDADE ESTADUAL DE CAMPINAS

Subjects
Cristais, Artigo original, Elétrons, Electrons, Ab initio calculations, Cálculos ab initio, Interpolação, Crystals, Interpolation
Abstract

Agradecimentos: The authors thank the Harvard FAS Research Computing facility and the Brazilian CCJDR-IFGW-UNICAMP for computational resources. A.S.C. and A.A. gratefully acknowledge financial support from the Brazilian agency FAPESP under Grant No. 2015/26434-2, No. 2016/23891-6, No. 2017/26105-4, No. 2018/01274-0, and No. 2019/26088-8. A.S.C. also acknowledges the kind hospitality of Harvard John A. Paulson School of Engineering and Applied Sciences Abstract: The coupling between electrons and phonons in solids plays a central role in describing many phenomena, including superconductivity and thermoelectric transport. Calculations of this coupling are exceedingly demanding as they necessitate integrations over both the electron and phonon momenta, both of which span the Brillouin zone of the crystal, independently. We present here an ab initio method for efficiently calculating electron-phonon mediated transport properties by dramatically accelerating the computation of the double integrals with a dual interpolation technique that combines maximally localized Wannier functions with symmetry-adapted plane waves. The performance gain in relation to the current state-of-the-art Wannier-Fourier interpolation is approximately 2n(s) x M, where n, is the number of crystal symmetry operations and M, a number in the range 5-60, governs the expansion in star functions. We demonstrate with several examples how our method performs some ab initio calculations involving electron-phonon interactions FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Published
2020

41. Density functional investigation of the adsorption effects of PH3 and SH2 on the structure stability of the Au55 and Pt55 nanoclusters.

Author

Guedes-Sobrinho, Diego, Chaves, Anderson S., Piotrowski, Maurício J., and Da Silva, Juarez L. F.

Subjects
*METAL clusters, *DENSITY functional theory, *ADSORBATES, *ADSORPTION (Chemistry), *ICOSAHEDRA
Abstract

Although several studies have been reported for Pt55 and Au55 nanoclusters, our atomistic understanding of the interplay between the adsorbate-surface interactions and the mechanisms that lead to the formation of the distorted reduced core (DRC) structures, instead of the icosahedron (ICO) structure in gas phase, is still far from satisfactory. Here, we report a density functional theory (DFT) investigation of the role of the adsorption effects of PH3 (one lone pair of electrons) and SH2 (two lone pairs) on the relative stability of the Pt55 and Au55 nanoclusters. In gas phase, we found that the DRC structures with 7 and 9 atoms in the core region are about 5.34 eV (Pt55) and 2.20 eV (Au55) lower in energy than the ICO model with Ih symmetry and 13 atoms in the core region. However, the stability of the ICO structure increases by increasing the number of adsorbed molecules from 1 to 18, in which both DRC and ICO structures are nearly degenerate in energy at the limit of 18 ligands, which can be explained as follows. In gas phase, there is a strong compression of the cationic core region by the anionic surface atoms induced by the attractive Coulomb interactions (core+-surface-), and hence, the strain release is obtained by reducing the number of atoms in the cationic core region, which leads to the 55 atoms distorted reduced core structures. Thus, the Coulomb interactions between the core+ and surface- contribute to break the symmetry in the ICO55 structure. On the other hand, the addition of ligands on the anionic surface reduces the charge transfer between the core and surface, which contributes to decrease the Coulomb interactions and the strain on the core region of the ICO structure, and hence, it stabilizes a compact ICO structure. The same conclusion is obtained by adding van der Waals corrections to the plain DFT calculations. Similar results are obtained by the addition of steric effects, which are considered through the adsorption of triphenylphosphine (PPh3) molecules on Au55, in which the relative stability between ICO and DRC is the same as for PH3 and SH2. However, for Pt55, we found an inversion of stability due to the PPh3 ligand effects, where ICO has higher stability than DRC by 2.40 eV. Our insights are supported by several structural, electronic, and energetic analyses. [ABSTRACT FROM AUTHOR]

Published
2017
Full Text
View/download PDF

43. INFLUÊNCIA DAS CONDIÇÕES DE REAÇÃO NA PRODUÇÃO DE NANOPARTÍCULAS NO GRAU DE ENCAPSULAMENTO DO CARDANOL

Author

Valério, Roberta Bussons Rodrigues, primary, Silva, Nilvan Alves da, additional, Paiva Junior, José Ribamar, additional, Ferreira, Valéria Maria Sousa, additional, Chaves, Anderson Valério, additional, Forte, Maria Madalena de Camargo, additional, Morais, Selene Maia, additional, and Abreu, Flávia Oliveira Monteiro da Silva, additional

Published
2020
Full Text
View/download PDF

45. ESTUDO ESPECTROSCÓPICO DO COMPLEXO [CO(NH3)6]CL2 A PARTIR DO CLORETO DE COBALTO (II) COMO PROPOSTA DE PRÁTICA PARA DISCIPLINA DE QUÍMICA INORGÂNICA III / SPECTROSCOPIC STUDY OF THE COMPLEX [CO (NH3) 6] CL2 FROM COBALT (II) CHLORIDE AS A PRACTICE PROPOSAL FOR INORGANIC CHEMISTRY DISCIPLINE III

Author

Oliveira, Luciana Mendonça de, primary, Chaves, Anderson Valério, additional, Valério, Roberta Bussons Rodrigues, additional, Silva, Wildson Max Barbosa da, additional, Nascimento, Guida Hellen Mota do, additional, and Pinheiro, Solange de Oliveira, additional

Published
2020
Full Text
View/download PDF

50. A theoretical investigation of the structural and electronic properties of 55-atom nanoclusters: The examples of Y-Tc and Pt.

Author

Batista, Krys E. A., Piotrowski, Maurício J., Chaves, Anderson S., and Da Silva, Juarez L. F.

Subjects
ATOMIC clusters, ELECTRIC properties, SURFACE chemistry, TRANSITION metals, DENSITY functional theory, POLAR effects (Chemistry)
Abstract

Several studies have found that the Pt55 nanocluster adopts a distorted reduced core structure, DRC55, in which there are 8-11 atoms in the core and 47-44 atoms in the surface, instead of the compact and high-symmetry icosahedron structure, ICO55, with 13 and 42 atoms in the core and surface, respectively. The DRC structure has also been obtained as the putative global minimum configuration (GMC) for the Zn55 (3d), Cd55 (4d), and Au55 (5d) systems. Thus, the DRC55 structure has been reported only for systems with a large occupation of the d-states, where the effects of the occupation of the valence anti-bonding d-states might play an important role. Can we observe the DRC structure for 55-atom transition-metal systems with non-occupation of the anti-bonding d-states? To address this question, we performed a theoretical investigation of the Y55, Zr55, Nb55, Mo55, Tc55, and Pt55 nanoclusters, employing density functional theory calculations. For the putative GMCs, we found that the Y55 adopts the ICO55 structure, while Nb55 and Mo55 adopt a bulk-like fragment based on the hexagonal close-packed structure and Tc55 adopts a face-centered cubic fragment; however, Zr55 adopts a DRC55 structure, like Zn55, Cd55, Pt55, and Au55. Thus we can conclude that the preference for DRC55 structure is not related to the occupation of the anti-bonding d-states, but to a different effect, in fact, a combination of structural and electronic effects. Furthermore, we obtained that the binding energy per atom follows the occupation of the bonding and anti-bonding model, i.e., the stability of the studied systems increases from Y to Tc with a small oscillation for Mo, which also explains the equilibrium bond lengths. We obtained a larger magnetic moment for Y55 (31 μB) which can be explained by the localization of the d-states in Y at nanoscale, which is not observed for the remaining systems (0-1 μB). [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results