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Your search keyword '"Penev, Evgeni S."' showing total 182 results
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182 results on '"Penev, Evgeni S."'

1. Stability and electronic properties of two-dimensional gallium

Author

Kutana, Alex, Ruan, Qiyuan, Zhang, Jun-Jie, Penev, Evgeni S., and Yakobson, Boris I.

Subjects
Condensed Matter - Materials Science
Abstract

Two-dimensional metals offer intriguing possibilities to explore metallicity and other related properties in systems with reduced dimensionality. Here, following recent experimental reports of synthesis of two-dimensional metallic gallium (gallenene) on insulating substrates, we conduct a computational search of gallenene structures using the Particle Swarm Optimization algorithm, and identify stable low energy structures. Our calculations of the critical temperature for conventional superconductivity yield values $\sim 7$ K for gallenene. We also emulate the presence of the substrate by introducing the external confining potential and test its effect on the structures with unstable phonons.

Published
2021

3. Elasticity, Flexibility and Ideal Strength of Borophenes

Author

Zhang, Zhuhua, Yang, Yang, Penev, Evgeni S., and Yakobson, Boris I.

Subjects
Condensed Matter - Materials Science
Abstract

We study the mechanical properties of two-dimensional (2D) boron, borophenes, by first-principles calculations. The recently synthesized borophene with 1/6 concentration of hollow hexagons (HH) is shown to have in-plane modulus C up to 210 N/m and bending stiffness as low as D = 0.39 eV. Thus, its Foppl-von Karman number per unit area, defined as C/D, reaches 568 nm-2, over twofold higher than graphene's value, establishing the borophene as one of the most flexible materials. Yet, the borophene has a specific modulus of 346 m2/s2 and ideal strengths of 16 N/m, rivaling those (453 m2/s2 and 34 N/m) of graphene. In particular, its structural fluxionality enabled by delocalized multi-center chemical bonding favors structural phase transitions under tension, which result in exceptionally small breaking strains yet highly ductile breaking behavior. These mechanical properties can be further tailored by varying the HH concentration, and the boron sheet without HHs can even be stiffer than graphene against tension. The record high flexibility combined with excellent elasticity in boron sheets can be utilized for designing composites and flexible systems., Comment: 13 pages, 5 figures

Published
2016
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5. Why do nanotubes grow chiral?

Author

Artyukhov, Vasilii I., Penev, Evgeni S., and Yakobson, Boris I.

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

Carbon nanotubes (CNT) hold enormous technological promise. It can only be harnessed if one controls in a practical way the CNT chirality, the feature of the tubular carbon topology that governs all the CNT properties---electronic, optical, mechanical. Experiments in catalytic growth over the last decade have repeatedly revealed a puzzling strong preference towards minimally-chiral (near-armchair) CNT, challenging any existing hypotheses and turning chirality control ever more tantalizing yet leaving its understanding elusive. Here we combine the CNT/catalyst interface thermodynamics with the kinetic growth theory to show that the unusual near-armchair peaks emerge from the two antagonistic trends: energetic preference towards achiral CNT/catalyst interfaces vs. faster growth of chiral CNT. This narrow distribution is profoundly related with the peaked behavior of a simple function, x*exp(-x).

Published
2014
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6. Probing the Synthesis of Two-Dimensional Boron by First-Principles Computations

Author

Liu, Yuanyue, Penev, Evgeni S., and Yakobson, Boris I.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Boron synthesis, in theory: Although two-dimensional boron sheets have attracted considerable interest because of their theoretically predicted properties, synthesis of such sheets remains a challenge. The feasibility of different synthetic methods for two-dimensional boron sheets was assessed using first-principles calculations, possibly paving the way towards its application in nanoelectronics.

Published
2013
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8. Specific Heat Discontinuity in Impure Two-Band Superconductors

Author

Mishonov, Todor M., Penev, Evgeni S., Indekeu, Joseph O., and Pokrovsky, Valery L.

Subjects
Condensed Matter - Superconductivity
Abstract

The Ginzburg-Landau coefficients, and the jump of the specific heat are calculated for a disordered two-band superconductor. We start with the analysis of a more general case arbitrary anisotropy. While the specific heat discontinuity at the critical temperature T_c decreases with increasing disorder, its ratio to the normal state specific heat at T_c increases and slowly converges to the isotropic value. For a strong disorder the deviation from the isotropic value is proportional to the elastic electron scattering time. In the case of a two-band superconductor we apply a simplified model of the interaction independent on momentum within a band. In the framework of this model all thermodynamic values can be found explicitly at any value of the scattering rate. This solution explains the sample dependence of the specific heat discontinuity in MgB_2 and the influence of the disorder on the critical temperature., Comment: New results relate to two-band superconductors, 9 pages, 2 figures

Published
2002
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9. Comment on 'Anisotropic s-wave superconductivity in MgB_2'

Author

Mishonov, Todor M., Penev, Evgeni S., and Indekeu, Joseph O.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Materials Science
Abstract

An analytical result for renormalization of the jump of the heat capacity Delta C/C_N by the anisotropy of the order parameter is derived in the framework of the model proposed by Haas and Maki [Phys. Rev. B 65, 020502(R) (2001)], for both prolate and oblate anisotropy. The graph of Delta C/C_N versus the ratio of the gaps on the equator and the pole, Delta_e/Delta_p, of the Fermi surface allows a direct determination of the gap anisotropy parameter Delta_e/Delta_p using data from specific heat measurements., Comment: 1 page, 1 figure, REVTeX 4, to be submitted to Phys. Rev. B

Published
2002
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21. A jellium model of a catalyst particle in carbon nanotube growth.

Author

Artyukhov, Vasilii I., Mingjie Liu, Penev, Evgeni S., and Yakobson, Boris I.

Subjects
CARBON nanotubes, CATALYSTS, GROWTH factors, PENTAGONS, HEPTAGON, DENSITY functional theory
Abstract

We show how a jellium model can represent a catalyst particle within the density-functional theory based approaches to the growth mechanism of carbon nanotubes (CNTs). The advantage of jellium is an abridged, less computationally taxing description of the multi-atom metal particle, while at the same time in avoiding the uncertainty of selecting a particular atomic geometry of either a solid or ever-changing liquid catalyst particle. A careful choice of jellium sphere size and its electron density as a descriptive parameter allows one to calculate the CNT-metal interface energies close to explicit full atomistic models. Further, we show that using jellium permits computing and comparing the formation of topological defects (sole pentagons or heptagons, the culprits of growth termination) as well as pentagon-heptagon pairs 517 (known as chirality-switching dislocation). [ABSTRACT FROM AUTHOR]

Published
2017
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23. Iron corrosion in the “inert” supercritical CO2, ab initiodynamics insights: How impurities matter

Author

Li, Qin-Kun, Kutana, Alex, Penev, Evgeni S., and Yakobson, Boris I.

Abstract

Metal corrosion from exposure to supercritical fluids is a long-standing challenge lacking atomistic understanding for effective corrosion prevention in diverse important applications. Here, reactions relevant to corrosion in supercritical CO2(sCO2), with H2O and NO2as impurities, are revealed using ab initiomolecular dynamics and enhanced sampling methods. While little reactivity is observed in bulk sCO2, the iron surface is found to play a crucial almost-catalytic role in its own corrosion, activating the inert CO2and hence facilitating ∗HCO3−and ∗CO32−formation at the interface. Moreover, the hydrogen bond network of ∗H2O assists the H shuttling to the activated CO2and impurities, forming reactive species observed in experiments. Such atomistic insight elucidates the reaction mechanisms of metal corrosion in aqueous and supercritical fluids and can point to possible remedies.

Published
2022
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24. Carbon Nanotubes and Related Nanomaterials

Author

Rao, Rahul, Pint, Cary L., Islam, Ahmad E., Weatherup, Robert S., Hofmann, Stephan, Meshot, Eric R., Wu, Fanqi, Zhou, Chongwu, Dee, Nicholas, Amama, Placidus B., Carpena-Nunez, Jennifer, Shi, Wenbo, Plata, Desiree L., Penev, Evgeni S., Yakobson, Boris I., Balbuena, Perla B., Bichara, Christophe, Futaba, Don N., Noda, Suguru, Shin, Homin, Kim, Keun Su, Simard, Benoit, Mirri, Francesca, Pasquali, Matteo, Fornasiero, Francesco, Kauppinen, Esko I., Arnold, Michael, Cola, Baratunde A., Nikolaev, Pavel, Arepalli, Sivaram, Cheng, Hui Ming, Zakharov, Dmitri N., Stach, Eric A., Zhang, Jin, Wei, Fei, Terrones, Mauricio, Geohegan, David B., Maruyama, Benji, Maruyama, Shigeo, Li, Yan, Adams, W. Wade, Hart, A. John, Wright-Patterson AFB, Vanderbilt University, University of Manchester, University of Cambridge, Lawrence Livermore National Laboratory, University of Southern California, Massachusetts Institute of Technology, Kansas State University, Yale University, Rice University, Texas A&M University, CNRS, National Institute of Advanced Industrial Science and Technology, Waseda University, National Research Council of Canada, NanoMaterials, University of Wisconsin-Madison, Georgia Institute of Technology, Tsinghua University, Brookhaven National Laboratory, University of Pennsylvania, Peking University, Pennsylvania State University, Oak Ridge National Laboratory, The University of Tokyo, Department of Applied Physics, Aalto-yliopisto, and Aalto University

Subjects
carbon nanotubes, synthesis, graphene, boron nitride nanotubes, 2D materials, chirality control, CVD, helicity
Abstract

Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.

Published
2018

25. Carbon Nanotubes and Related Nanomaterials: Critical Advances and Challenges for Synthesis toward Mainstream Commercial Applications

Author

Rao, Rahul, primary, Pint, Cary L., additional, Islam, Ahmad E., additional, Weatherup, Robert S., additional, Hofmann, Stephan, additional, Meshot, Eric R., additional, Wu, Fanqi, additional, Zhou, Chongwu, additional, Dee, Nicholas, additional, Amama, Placidus B., additional, Carpena-Nuñez, Jennifer, additional, Shi, Wenbo, additional, Plata, Desiree L., additional, Penev, Evgeni S., additional, Yakobson, Boris I., additional, Balbuena, Perla B., additional, Bichara, Christophe, additional, Futaba, Don N., additional, Noda, Suguru, additional, Shin, Homin, additional, Kim, Keun Su, additional, Simard, Benoit, additional, Mirri, Francesca, additional, Pasquali, Matteo, additional, Fornasiero, Francesco, additional, Kauppinen, Esko I., additional, Arnold, Michael, additional, Cola, Baratunde A., additional, Nikolaev, Pavel, additional, Arepalli, Sivaram, additional, Cheng, Hui-Ming, additional, Zakharov, Dmitri N., additional, Stach, Eric A., additional, Zhang, Jin, additional, Wei, Fei, additional, Terrones, Mauricio, additional, Geohegan, David B., additional, Maruyama, Benji, additional, Maruyama, Shigeo, additional, Li, Yan, additional, Adams, W. Wade, additional, and Hart, A. John, additional

Published
2018
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29. Thermal fluctuations in shape, thickness, and molecular orientation in lipid bilayers.

Author

Watson, Max C., Penev, Evgeni S., Welch, Paul M., and Brown, Frank L. H.

Subjects
*THERMAL analysis, *FLUCTUATIONS (Physics), *THICKNESS measurement, *BILAYER lipid membranes, *CONTINUUM mechanics, *BENDING (Metalwork), *MATERIALS compression testing, *MOLECULAR dynamics, *SIMULATION methods & models
Abstract

We present a unified continuum-level model for bilayer energetics that includes the effects of bending, compression, lipid orientation (tilting relative to the monolayer surface normal), and microscopic noise (protrusions). Expressions for thermal fluctuation amplitudes of several physical quantities are derived. These predictions are shown to be in good agreement with molecular simulations. [ABSTRACT FROM AUTHOR]

Published
2011
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35. Magnetic field controlled graphene oxide-based origami with enhanced surface area and mechanical properties

Author

Park, Ok-Kyung, primary, Tiwary, Chandra Sekhar, additional, Yang, Yang, additional, Bhowmick, Sanjit, additional, Vinod, Soumya, additional, Zhang, Qingbo, additional, Colvin, Vicki L., additional, Asif, S. A. Syed, additional, Vajtai, Robert, additional, Penev, Evgeni S., additional, Yakobson, Boris I., additional, and Ajayan, Pulickel M., additional

Published
2017
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45. Carbon Nanotubes: Controllable and Predictable Viscoelastic Behavior of 3D Boron‐Doped Multiwalled Carbon Nanotube Sponges (Part. Part. Syst. Charact. 1/2016)

Author

Zhao, Wenjie, primary, Elias, Ana L., additional, Rajukumar, Lakshmy P., additional, Kim, Hyung‐Ick, additional, O'Brien, Daniel J., additional, Zimmerman, Brandon K., additional, Penev, Evgeni S., additional, Terrones, Mauricio, additional, Yakobson, Boris I., additional, Wei, Bingqing, additional, Lu, X. Lucas, additional, and Suhr, Jonghwan, additional

Published
2016
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47. Controllable and Predictable Viscoelastic Behavior of 3D Boron-Doped Multiwalled Carbon Nanotube Sponges

Author

Zhao, Wenjie, primary, Elias, Ana L., additional, Rajukumar, Lakshmy P., additional, Kim, Hyung-Ick, additional, O'Brien, Daniel J., additional, Zimmerman, Brandon K., additional, Penev, Evgeni S., additional, Terrones, Mauricio, additional, Yakobson, Boris I., additional, Wei, Bingqing, additional, Lu, X. Lucas, additional, and Suhr, Jonghwan, additional

Published
2015
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48. Janus Segregation at the Carbon Nanotube–Catalyst Interface

Author

Bets, Ksenia V., Penev, Evgeni S., and Yakobson, Boris I.

Abstract

The contact between a carbon nanotube (CNT) edge and a catalyst is a curvilinear interface of fundamental and practical importance. Here, the first-principles evidence shows that on a rigid/solid catalyst the faceted CNT edge is significantly lower in energy compared to the minimal-length circle, with the interface energy difference decreasing on more compliant surfaces. This universal trend, found for typical monometallic (Ni, Co), bimetallic (Co7W6), and metal carbide (WC) catalysts, results in a peculiar edge segregation into one-dimensional Janus (armchair–zigzag) interface. Its lowered energy greatly enhances the nucleation probability of chiral tubes, dramatically affecting their growth kinetics. This offers a richer basis for understanding, modeling, and control of catalytic CNT synthesis.

Published
2019
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