34 results on '"Xin LU"'
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2. Electronic structure and hydrogen bond in the crystal of paracetamol drugs
- Author
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An, Guang-Wen, Zhang, Hong, Cheng, Xin-Lu, Zhuo, Quan-Lu, and Lv, Yi-Chao
- Published
- 2008
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3. Growth, electronic structure and superconductivity of ultrathin epitaxial CoSi2 films
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Tian Le, Chao Cao, Xin Lu, Yang Liu, Ding Wang, Peng Li, Yuan Fang, Yanwu Xie, Yi Wu, Yan-Qiu Sun, Si-Yuan Hong, Hang Su, Hua-Li Zhang, Huiqiu Yuan, Guo-Wei Yang, Zhiguang Xiao, and Huanhua Wang
- Subjects
Superconductivity ,Materials science ,Condensed matter physics ,Angle-resolved photoemission spectroscopy ,02 engineering and technology ,Electronic structure ,Electron ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Quantum dot ,0103 physical sciences ,General Materials Science ,Density functional theory ,Symmetry breaking ,010306 general physics ,0210 nano-technology ,Critical field - Abstract
We report growth, electronic structure and superconductivity of ultrathin epitaxial CoSi2 films on Si (111). At low coverages, preferred islands with 2, 5 and 6 monolayers height develop, which agrees well with the surface energy calculation. We observe clear quantum well states as a result of electronic confinement and their dispersion agrees well with density functional theory calculations, indicating weak correlation effect despite strong contributions from Co 3d electrons. Ex situ transport measurements show that superconductivity persists down to at least 10 monolayers, with reduced T c but largely enhanced upper critical field. Our study opens up the opportunity to study the interplay between quantum confinement, interfacial symmetry breaking and superconductivity in an epitaxial silicide film, which is technologically relevant in microelectronics.
- Published
- 2021
4. Crossover from a heavy fermion to intermediate valence state in noncentrosymmetric Yb2Ni12(P,As)7
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Tian Shang, Z. W. Cheng, H. Ishii, J. M. Chen, Fei Gao, Michael Smidman, J. M. Lee, Huiqiu Yuan, Lifei Yang, Cheng Guo, Zhiwei Hu, K. D. Tsuei, Liu Hao Tjeng, Xin Lu, Y. F. Liao, Yaofeng Wang, and Wei Jiang
- Subjects
Multidisciplinary ,Materials science ,Valence (chemistry) ,Condensed matter physics ,Absorption spectroscopy ,Strongly Correlated Electrons (cond-mat.str-el) ,FOS: Physical sciences ,Electronic structure ,Article ,Condensed Matter - Strongly Correlated Electrons ,Paramagnetism ,Magnetization ,Condensed Matter::Materials Science ,Electrical resistivity and conductivity ,Quantum critical point ,Condensed Matter::Strongly Correlated Electrons ,Fermi liquid theory - Abstract
We report measurements of the physical properties and electronic structure of the hexagonal compounds Yb2Ni12Pn7 (Pn = P, As) by measuring the electrical resistivity, magnetization, specific heat and partial fluorescence yield x-ray absorption spectroscopy (PFY-XAS). These demonstrate a crossover upon reducing the unit cell volume, from an intermediate valence state in Yb2Ni12As7 to a heavy-fermion paramagnetic state in Yb2Ni12P7, where the Yb is nearly trivalent. Application of pressure to Yb2Ni12P7 suppresses T_FL, the temperature below which Fermi liquid behavior is recovered, suggesting the presence of a quantum critical point (QCP) under pressure. However, while there is little change in the Yb valence of Yb2Ni12P7 up to 30 GPa, there is a strong increase for Yb2Ni12As7 under pressure, before a near constant value is reached. These results indicate that any magnetic QCP in this system is well separated from strong valence fluctuations. The pressure dependence of the valence and lattice parameters of Yb2Ni12As7 are compared and at 1 GPa, there is an anomaly in the unit cell volume as well as a change in the slope of the Yb valence, indicating a correlation between structural and electronic changes., Comment: 11 pages, 9 figures
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- 2015
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5. Spectroscopic evidence for two-gap superconductivity in the quasi-1D chalcogenide Nb2Pd0.81S5
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Luis Balicas, Eunsung Park, Tuson Park, Sangyun Lee, Joe D. Thompson, Qiu Zhang, Filip Ronning, and Xin Lu
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Superconductivity ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Chalcogenide ,02 engineering and technology ,Quantum phases ,Electronic structure ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Magnetic field ,Andreev reflection ,chemistry.chemical_compound ,chemistry ,Condensed Matter::Superconductivity ,0103 physical sciences ,General Materials Science ,010306 general physics ,0210 nano-technology ,Wave function - Abstract
Low-dimensional electronic systems with confined electronic wave functions have attracted interest due to their propensity toward novel quantum phases and their use in wide range of nanotechnologies. The newly discovered chalcogenide Nb2PdS5 possesses a quasi-one-dimensional electronic structure and becomes superconducting. Here, we report spectroscopic evidence for two-band superconductivity, where soft point-contact spectroscopic measurements in the superconducting (SC) state reveal Andreev reflection in the differential conductance G. Multiple peaks in G are observed at 1.8 K and explained by the two-band Blonder–Tinkham–Klapwijk model with two gaps Δ1 = 0.61 meV and Δ2 = 1.20 meV. The progressive evolution of G with temperature and magnetic field corroborates the multiple nature of the SC gaps.
- Published
- 2018
6. First principles study on the structure and electronic properties of 2-nitrimino-1-nitroimidazolidine
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Hong Zhang, Fu-Chun Zhang, Guang-Wen An, Xin-Lu Cheng, and Lian-Jun Xu
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Crystal ,Band gap ,Chemistry ,Hydrogen bond ,Density of states ,Electronic structure ,Physical and Theoretical Chemistry ,Local-density approximation ,SIESTA (computer program) ,Atomic physics ,Condensed Matter Physics ,Bond-dissociation energy ,Atomic and Molecular Physics, and Optics - Abstract
The properties of 2-Nitrimino-1-nitroimidazolidine are calculated by using SIESTA code, which adopts the standard Kohn-Sham self-consistent density functional method in the local density approximation. The structures and electronic properties are analyzed, and the factors that affect the impact sensitivity are discussed based on the crystal structure, band energy, and projected density of state. The reason for the smaller impact sensitivity compared to RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is also explored from several respects such as the weakest bond dissociation energy in single molecule, and hydrogen bond, band gap in the crystal. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
- Published
- 2009
7. Open-Shell Singlet Character of Cyclacenes and Short Zigzag Nanotubes
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Zhongfang Chen, Schleyer Pv, Sheng Dai, De-en Jiang, Xin Lu, Houk Kn, and Holger F. Bettinger
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Spins ,Chemistry ,Organic Chemistry ,Electronic structure ,Biochemistry ,Molecular physics ,Zigzag ,Computational chemistry ,Condensed Matter::Strongly Correlated Electrons ,Density functional theory ,Complete active space ,Singlet state ,Physical and Theoretical Chemistry ,Perturbation theory ,Open shell - Abstract
The electronic ground states of [n]cyclacenes, as well as short-zigzag nanotubes, computed at unrestricted broken spin-symmetry density functional theory (UBS-DFT), were found to be open-shell singlets, rather than triplets. Computations for [6]cyclacene at complete active space self-consistent field (CASSCF) and multireference perturbation theory (MRMP2) levels support this conclusion. Along with strain, the radical character of the open-shell singlet with antiferromagnetically coupled electron spins may contribute to the difficulties in synthesizing [n]cyclacenes.
- Published
- 2007
8. Comparative Spectroscopic and Reactivity Studies of Sc3-xYxN@C80 (x = 0−3)
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Xin Lu, Kai Tan, Yue-Qin Wu, Chun-Ying Shu, Chunru Wang, Ning Chen, and Lou-Zhen Fan
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chemistry.chemical_element ,Electronic structure ,Mass spectrometry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Crystallography ,General Energy ,chemistry ,Computational chemistry ,symbols ,Endohedral fullerene ,Van der Waals radius ,Reactivity (chemistry) ,Differential pulse voltammetry ,Scandium ,Physical and Theoretical Chemistry ,Fourier transform infrared spectroscopy - Abstract
A series of endohedral fullerenes Sc3-xYxN@C80 (x = 0−3) with variable encaged moieties and the same C80 cage were synthesized, isolated, and spectroscopically characterized by the laser desorption time-of-flight mass spectrometry (LD-TOF−MS), differential pulse voltammetry (DPV), Fourier transform infrared (FTIR), visible-near-infrared (vis-NIR) absorption spectrometry, and so forth. It was revealed that Sc3-xYxN@C80 (x = 0−3) have a similar electronic structure, (Sc3-xYxN)6+@(C80)6-. However, because of the relatively larger van der Waals radius of yttrium to that of scandium which induces the size increase of Sc3-xYxN from x = 0 to x = 3, the frontier orbitals of this series of endohedral fullerenes dramatically change. For example, Sc2YN@C80 shows similar electronic property with its left neighbor Sc3N@C80 but is quite different with its right neighbor ScY2N@C80. The cycloaddition reactions of N-enthylazomethine ylide with Sc3-xYxN@C80 (x = 0−3) were carried out, and the regioselectivity of endohedral...
- Published
- 2007
9. Electronic Structure and Redox Properties of the Open-Shell Metal−Carbide Endofullerene Sc3C2@C80: A Density Functional Theory Investigation
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Xin Lu and Kai Tan
- Subjects
Metal ,Valence (chemistry) ,Computational chemistry ,Chemical physics ,Chemistry ,visual_art ,visual_art.visual_art_medium ,Density functional theory ,Electronic structure ,Physical and Theoretical Chemistry ,Open shell ,Redox ,Carbide - Abstract
Density functional theory calculations have shown that the open-shell metal-carbide endofullerene Sc3C2@C80 has the valence state (Sc3+)3(C2)(3-)@C80(6-). A lot of low-lying isomers differing in geometries and locations of the endohedral [(Sc3+)3(C2)(3-)] cluster have been located, indicating unusual dual intramolecular dynamic behaviors of this endofullerene at room temperature. The electrochemical redox properties of this endofullerene have been elucidated in terms of electronic structure theory. Its redox states are found to follow the general charge-state formula (Sc3+)3C2(3-q)-@C80(6-) (q is the charge of the whole molecule ranging from +1 to -3), demonstrating the high charge flexibility of the endohedral metal-carbide cluster. The structure of the endohedral [(Sc3+)3C2(3-q)-)] cluster varies with the redox processes, shifting from a planar structure (for q = 0 and -1) to a trifoliate structure (for q = +1, -2, -3).
- Published
- 2006
10. Suppression of antiferromagnetism by pressure inCaCo2P2
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Brian L. Scott, Eve Bauer, Darrick J. Williams, V. A. Sidorov, Nirmal Ghimire, Filip Ronning, Xin Lu, Ryan Baumbach, and J. D. Thompson
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Quantum phase transition ,Physics ,Paramagnetism ,Magnetization ,Phase transition ,Condensed matter physics ,Antiferromagnetism ,Electronic structure ,Condensed Matter Physics ,Heat capacity ,Electronic, Optical and Magnetic Materials ,Phase diagram - Abstract
We report magnetization $M$, heat capacity $C$, and electrical resistivity $\ensuremath{\rho}$ for single crystals of the itinerant electron antiferromagnet ${\text{CaCo}}_{2}$${\text{P}}_{2}$ (${T}_{\mathrm{N}}$ $\ensuremath{\approx}$ 110 K). Measurements at ambient pressure reveal rich magnetic behavior, where ferromagnetic correlations are present in the paramagnetic state and a subsequent feature is seen at ${T}_{1}$ $\ensuremath{\approx}$ 22 K within the ordered state. Heat-capacity measurements additionally reveal moderately enhanced electronic correlations, as evidenced by the electronic coefficient of the specific heat $\ensuremath{\gamma}$ $=$ 23 mJ$/$mol$\ifmmode\cdot\else\textperiodcentered\fi{}$K${}^{2}$, which is large by comparison to closely related 122 analogs and the value predicted by electronic structure calculations. Upon the application of pressure, ${T}_{\mathrm{N}}$ is suppressed toward zero. For $P$ $\ensuremath{\ge}$ 0.89 GPa, another phase transition appears at ${T}_{2}$ $l$ ${T}_{\mathrm{N}}$ which is also suppressed by $P$. At ${P}_{\mathrm{c}}$ $\ensuremath{\approx}$ 1.4--1.5 GPa, ${T}_{\mathrm{N}}$ and ${T}_{2}$ drop abruptly to zero at a putative quantum phase transition. For $P$ $g$ ${P}_{\mathrm{c}}$, a broad shoulder in $\ensuremath{\rho}(T)$ appears at ${T}^{*}$, which moves to higher $T$ and broadens with increasing $P$. We discuss possible scenarios to understand the phase diagram and compare to other compounds which show similar $P$-driven behavior.
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- 2014
11. Detection of DNA Bases Using Fe Atoms and Graphene
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Wen-Xing Zhang, Ya-Xin Lu, Jian-Fen Hu, Yong Li, and Lin Feng
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Materials science ,Magnetic moment ,Guanine ,Graphene ,General Physics and Astronomy ,02 engineering and technology ,Electronic structure ,equipment and supplies ,021001 nanoscience & nanotechnology ,01 natural sciences ,Thymine ,Nucleobase ,law.invention ,chemistry.chemical_compound ,Crystallography ,Adsorption ,chemistry ,law ,0103 physical sciences ,Atomic physics ,010306 general physics ,0210 nano-technology ,human activities ,Cytosine - Abstract
The adsorption of DNA bases on a magnetic probe composed of Fe atoms and graphene is studied by using first-principles calculations. The stability of geometry, the electronic structure and magnetic property are investigated. The results indicate that four DNA bases, i.e., adenine, thymine, cytosine and guanine, can all be adsorbed on the probe solidly. However, the magnetic moments of the composite structure can be observed only when adenine adsorbs on the probe. In the cases of the adsorption of the other three bases, the magnetic moments of the composite structure are zero. Based on the significant change of magnetic moment of the composite structure, adenine can be distinguished conveniently from thymine, cytosine and guanine. This work may provide a new way to detect DNA bases.
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- 2016
12. Unprecedented mu4-C2(6-) anion in Sc4C2@C80
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Kai Tan, Chunru Wang, and Xin Lu,† and
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Computational chemistry ,Chemistry ,Electron affinity ,Chemical shift ,Materials Chemistry ,Moiety ,Electronic structure ,Physical and Theoretical Chemistry ,Carbon-13 NMR ,Ionization energy ,Electrochemistry ,Surfaces, Coatings and Films ,Ion - Abstract
Metal carbide compound containing highly charged C2(q-) (q = 5, 6) moiety is rather scarce. We show by means of density functional calculations that an unprecedented mu4-C2(6-) anion can viably exist as an endohedral [Sc4C2]6+ cluster in the endofullerene Sc4C2@C80. The electronic structure, ionization energy, electron affinity, 13C NMR chemical shifts, vibrational frequencies, and electrochemical redox potentials of this unique endofullerene have been predicted to assist future experimental characterization.
- Published
- 2006
13. Electronic structure and optical properties of rutile RuO 2 from first principles
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Li Jin, Dai Wei, Yang Xiang-Dong, Cheng Xin-Lu, Guo Yun-Dong, Yang Ze-Jin, and Liu Jin-chao
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Bulk modulus ,Materials science ,Condensed matter physics ,business.industry ,General Physics and Astronomy ,Ionic bonding ,Dielectric ,Electronic structure ,Pseudopotential ,Condensed Matter::Materials Science ,Optics ,Density functional theory ,Pseudogap ,business ,Refractive index - Abstract
The systematic trends of electrionic structure and optical properties of rutile (P42/mnm) RuO2 have been calculated by using the plane-wave norm-conserving pseudopotential density functional theory (DFT) method within the generalised gradient approximation (GGA) for the exchange–correlation potential. The obtained equilibrium structure parameters are in excellent agreement with the experimental data. The calculated bulk modulus and elastic constants are also in good agreement with the experimental data and available theoretical calculations. Analysis based on electronic structure and pseudogap reveals that the bonding nature in RuO2 is a combination of covalent, ionic and metallic bonds. Based on a Kramers–Kronig analysis of the reflectivity, we have obtained the spectral dependence of the real and imaginary parts of the complex dielectric constant (1 and 2, respectively) and the refractive index (n); and comparisons have shown that the theoretical results agree well with the experimental data as well. Meanwhile, we have also calculated the absorption coefficient, reflectivity index, electron energy loss function of RuO2 for radiation up to 30 eV. As a result, the predicted reflectivity index is in good agreement with the experimental data at low energies.
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- 2010
14. First-principles calculation of p-Zn1-xMgxO electronic structure by doping with Al and N
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Liu Qiang, Cheng Xin-Lu, Fan Yong-Heng, and Yang Xiang-Dong
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Materials science ,Condensed matter physics ,Doping ,General Physics and Astronomy ,Electronic structure - Abstract
The first principles calculation of plane wave ultra-soft pseu-dopotential method based upon the denstiy functional theory and generalized gradient approximation have been adopted to investigate the energy band structure and electronic density of states and Mulilken charge population of Al and N codoped Zn1-xMgxO. The calculation indicates that the Al and N codoped Zn1-xMgxO has the trend of forming p-type Zn1-xMgxO.
- Published
- 2009
15. Theoretical investigations of structural, elastic and electronic properties of M2N3 (M = Zr, Hf, W and Re) with U2S3 structure.
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Zhang, Ji-Dong and Cheng, Xin-Lu
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CRYSTAL structure , *ELECTRONIC structure , *ELASTICITY , *NITRIDES , *DENSITY functional theory , *MODULUS of rigidity , *ZIRCONIUM compounds - Abstract
The structural, elastic and electronic properties of four nitrides M 2 N 3 (M = Zr, Hf, W and Re) with U 2 S 3 structure are investigated by plane-wave pseudopotential density functional theory by the generalized gradient approximation in this paper. The calculated elastic constants show that the nitrides are mechanically stable at ambient conditions, except Re 2 N 3 . The calculated bulk modulus B and shear modulus G indicate that Zr 2 N 3 , Hf 2 N 3 and W 2 N 3 are potential candidates for hard materials. [ABSTRACT FROM AUTHOR]
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- 2015
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16. First-principles study of the electronic structure and optical properties of cubic Perovskite NaMgF3.
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Zhen-Li, Li, Xin-You, An, Xin-Lu, Cheng, Xue-Min, Wang, Hong, Zhang, Li-Ping, Peng, and Wei-Dong, Wu
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ELECTRIC properties ,PEROVSKITE ,ELECTRONIC structure ,OPTICAL properties ,PLANE wavefronts ,PSEUDOPOTENTIAL method - Abstract
The structural, electronic, and optical properties of cubic perovskite NaMgF
3 are calculated by plane-wave pseudopotential density functional theory. The calculated lattice constant a0 , bulk modulus B0 , and the derivative of bulk modulus B′0 are 3.872 Å, 78.2 GPa, and 3.97, respectively. The results are in good agreement with the available experimental and theoretical values. The electronic structure shows that cubic NaMgF3 is an indirect insulator with a wide forbidden band gap of Eg = 5.90 eV. The contribution of the different bands is analyzed by total and partial density of states curves. Population analysis of NaMgF3 indicates that there is strong ionic bonding in the MgF2 unit, and a mixture of ionic and weak covalent bonding in the NaF unit. Calculations of dielectric function, absorption coefficient, refractive index, electronic energy loss spectroscopy, optical reflectivity, and conductivity are also performed in the energy range 0 to 70 eV. [ABSTRACT FROM AUTHOR]- Published
- 2014
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17. First-principles study of Ar adsorptions on the (111) surfaces of Pd, Pt, Cu, and Rh.
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Niu Wen-Xia, Zhang Hong, Gong Min, and Cheng Xin-Lu
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DENSITY functionals ,ELECTRONIC structure ,BINDING energy ,ATOMS ,SEPARATION technology equipment - Abstract
In the present paper we give a detailed report on the results of our first-principles investigations of Ar adsorptions at the four high symmetry sites on M (111) (M = Pd, Pt, Cu, and Rh) surfaces. Our studies indicate that the most stable adsorption sites of Ar on Pd (111) and Pt (111) surfaces are found to be the fcc-hollow sites. However, for Ar adsorptions on Cu (111) and Rh (111) surfaces, the most favorable site is the on-top site. The density of states (DOS) is analyzed for Ar adsorption on M (111) surfaces, and it is concluded that the adsorption behavior is dominated by the interaction between 3s, 3p orbits of Ar atoms and the d orbit of the base metal atoms. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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18. H2 ADSORPTION ON LiB (001) SURFACE: A FIRST PRINCIPLES CALCULATION.
- Author
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Zhang Wei-Bin, Wu Wei-Dong, Cheng Xin-Lu, Wang Xue-Min, Wang Hai-Ping, and An Xin-Youf
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HYDROGEN absorption & adsorption ,LITHIUM compounds ,ELECTRONIC band structure ,DENSITY functionals ,CHEMICAL bonds ,SURFACES (Technology) ,FORCE & energy ,BAND gaps - Abstract
The adsorption behavior of H
2 on the LiB (001) surface was investigated with density functional theory (DFT) method. It was found that the site of H2 adsorbed on the Li-B bridge II was easier than the other four sites (Li top, B top, hollow vertical and Li-B bridge I). H2 adsorbed on the Li-B bridge II site was a strong chemical adsorption. The adsorption energy was 2.190 eV, and the H, B atoms exhibited covalent characteristics, the H--H atoms have a little interaction, and the H2 was 0.331 Å below the surface of Li-B bridge II. The charge density, band structure, totals and partial density of states were calculated utilizing the first principle method. These calculations showed that the H interacted with the surface atoms, and partially saturated the dangling bonds with the surface atoms. The interaction between H and the surface atoms were mainly attributed to the H 1s, B 2s and B 2p states. The calculated band gap was 0.075 eV and 0.199 eV before and after adsorption. [ABSTRACT FROM AUTHOR]- Published
- 2012
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19. Orbital responses to methyl sites in CnH2n+2 (n = 1 6).
- Author
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Yang Ze-Jin, Cheng Xin-Lu, Zhu Zheng-He, and Yang Xiang-Dong
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MOLECULAR orbitals , *IONIZATION (Atomic physics) , *CARBON-carbon bonds , *MOMENTUM distributions , *VALENCE (Chemistry) , *ISOMERS , *ELECTRONIC structure , *PROPANE , *MATHEMATICAL models - Abstract
Orbital responses to methyl sites in CnH2n+2 (n = 1-6) are studied by B3LYP/TZVP based on the most stable geometries using the B3LYP/aug-cc-pVTZ method. Vertical ionization energies are produced using the SAOP/et-pVQZ model for the complete valence space. The highest occupied molecular orbital (HOMO) investigations indicate the pelectron profiles in methane, ethane, propane, and n-butane. By increasing the number of carbon-carbon bonds in lower momentum regions, the s, p-hybridized orbitals are built and display strong exchange and correlation interactions in lower momentum space (P . 0.50 a.u.). Meanwhile, the relative intensities of the isomers in lower momentum space show the strong bonding number dependence of the carbon-carbon bonds, meaning that more electrons have contributed to orbital construction. The study of representative valence orbital momentum distribution further confirms that the structural changes lead to evident electronic rearrangement over the whole valence space. An analysis based on the isomers reveals that the valence orbitals are isomer-dependent and the valence ionization energy experiences an apparent shift in the inner valence space. However, such shifts are greatly reduced in the outer valence space. Meanwhile, the opposite energy shift trend is found in the intermediate valence space. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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20. Heat-Capacity Measurements of Energy-Gap Nodes of the Heavy-Fermion Superconductor CeIrIn5 Deep inside the Pressure-Dependent Dome Structure of Its Superconducting Phase Diagram.
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Xin Lu, Hanoh Lee, Park, T., Ronning, F., Bauer, E. D., and Thompson, J. D.
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CESIUM compounds , *SUPERCONDUCTIVITY , *PRESSURE , *ELECTRONIC structure , *MATHEMATICAL models , *SPECTRUM analysis - Abstract
We use heat-capacity measurements as a function of field rotation to identify the nodal gap structure of CeIrIn5 at pressures to 2.05 GPa, deep inside its superconducting dome. A fourfold oscillation in the heat capacity at 0.3 K is observed for all pressures, but with its sign reversed between 1.50 and 0.90 GPa. On the basis of recent theoretical models for the field-angle-dependent specific heat, all data, including the sign reversal, imply a Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. order parameter with nodes along [110], which constrains theoretical models of the pairing mechanism in CeIrIn5. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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21. A first-principles investigation of the hydrogen bond interaction and the sensitive characters in cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole.
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Chen, Fang and Cheng, Xin‐Lu
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HYDROGEN bonding , *IMIDAZOLES , *MOLECULAR structure , *DENSITY functionals , *DISSOCIATION (Chemistry) , *ATOMIC orbitals , *SENSITIVITY analysis , *BAND gaps - Abstract
A theoretical study of structural and electronic properties of cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) crystal is performed using density functional theory. The band structure, the total density of states, the atomic orbit projected density of states (PDOS) of C, N, O, and H, and Mulliken population analysis are discussed. The study by analyzing the PDOS shows that the structure of BCHMX crystal possesses CH···O intra- and intermolecular hydrogen bonding. There are hydrogen bonds between H3-1s and O5-2p orbits, H2-1s and O6-2p orbits of intramolecules and between H2-1s and O1-2p orbits of intermolecules. The reasons for the smaller impact sensitivity compared with β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane and 1,3,5-trinitro-1,3,5-triazinane are also explored from the band gap in the crystal and the weakest bond dissociation energy in single molecule. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]
- Published
- 2011
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22. Optical properties of superhard BC5: First-principles calculations
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Zhang, Ji-Dong, Cheng, Xin-Lu, and Li, De-Hua
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OPTICAL properties , *NUMERICAL calculations , *DIELECTRICS , *ELECTRONIC structure , *ANISOTROPY , *DENSITY functionals , *APPROXIMATION theory , *ELECTRON energy loss spectroscopy - Abstract
Abstract: BC5 is a newly synthesized superhard material. We present a systematic investigation of optical properties of BC5 in P3m1 and I-4m2 phases at ambient and high pressure in the framework of density functional theory with the generalized gradient approximation (GGA) in this paper. Optical properties such as dielectric function, refractive index, absorption, reflectivity and electron energy-loss spectrum are obtained successfully. The feature in the spectra of the optical parameters is discussed. Through calculation, we find BC5 is optically anisotropic. Moreover, the dielectric function exhibits a large change at 70GPa pressure for P3m1 BC5 phase, but I-4m2 phase not, indicating the stable electronic structure that the I-4m2 phase possesses. [Copyright &y& Elsevier]
- Published
- 2011
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23. First-principles calculations of structural, elastic and electronic properties of TaB2 with AlB2 structure under high pressure
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Zhang, Ji-Dong, Cheng, Xin-Lu, and Li, De-Hua
- Subjects
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ELECTRONIC structure , *ELASTICITY , *TANTALUM , *HIGH pressure (Science) , *DENSITY functionals , *TEMPERATURE - Abstract
Abstract: We present a systematic theoretical study for the structural, elastic and electronic properties of TaB2 with AlB2 structure under pressures ranging from 0GPa to 120GPa within the framework of density-functional theory in this paper. The results at zero pressure are in good agreement with available theoretical and experimental values. Our attention has been focused on high pressure behavior of TaB2. The pressure dependence of structure, elastic constants, Debye temperature, and density of states (DOS) are successfully calculated and discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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24. The predicted structural and electronic properties of HfB2 under high pressure: First-principles calculations
- Author
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Zhang, Ji-Dong and Cheng, Xin-Lu
- Subjects
- *
ELECTRONIC structure , *ENERGY levels (Quantum mechanics) , *ELECTRIC properties of metals , *HAFNIUM , *DENSITY functionals , *CHARGE transfer , *BORON compounds , *NUMERICAL calculations - Abstract
Abstract: A systematic theoretical study is presented for the structural and electronic properties of HfB2 with AlB2 structure under pressure ranging from 0 to 240GPa in the framework of density functional theory. The results at zero pressure are in good agreement with the available theoretical and experimental values. The pressure dependence of structural property shows that the effect of pressure is little on the structure of HfB2. The density of states (DOS) of HfB2 versus pressure is also successfully calculated. We find high pressure greatly changes the profile of the DOS, but it hardly changes the DOS value at Fermi level. Meanwhile, the Mulliken population analyses are investigated. It is suggested that as the pressure increases, a number of charge transfer from Hf to B atoms. [Copyright &y& Elsevier]
- Published
- 2010
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25. First principles study on the structure and electronic properties of 2-nitrimino-1-nitroimidazolidine.
- Author
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Zhang, Hong, Xu, Lian‐Jun, Zhang, Fu‐Chun, Cheng, Xin‐Lu, and An, Guang‐Wen
- Subjects
DENSITY functionals ,DENSITY ,PROPERTIES of matter ,ATMOSPHERIC density ,CRYSTALS ,TRIAZINES ,ALKYLATING agents ,HYDROGEN bonding ,MOLECULAR association - Abstract
The properties of 2-Nitrimino-1-nitroimidazolidine are calculated by using SIESTA code, which adopts the standard Kohn-Sham self-consistent density functional method in the local density approximation. The structures and electronic properties are analyzed, and the factors that affect the impact sensitivity are discussed based on the crystal structure, band energy, and projected density of state. The reason for the smaller impact sensitivity compared to RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is also explored from several respects such as the weakest bond dissociation energy in single molecule, and hydrogen bond, band gap in the crystal. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
26. A DFT study on the electronic structure for iridium nitride under high pressure.
- Author
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Qi-lei Li, Hong Zhang, and Xin-Lu Cheng
- Subjects
DENSITY functionals ,ELECTRONIC structure ,NITRIDES ,IRIDIUM ,HIGH pressure chemistry ,CRYSTAL lattices ,BAND gaps ,ELECTRON distribution - Abstract
Abstract We present density functionary theory (DFT) calculations on the structural parameters and electronic structure for iridium nitride by using the generalized gradient approximation (GGA) and the Perdew–Burke–Ernserhof (PBE) exchange-correlation functional. The lattice parameters and bulk modulus (B 0) for the ground state are obtained, and the energy band structure and electron densities of states (DOS) of IrN2 are presented. It is found that IrN2 has a very close indirect energy gap. There is a strong covalent bond between the two nearest N atoms. This gives rise to a very high elastic modulus of IrN2 and reveals the quasimolecular nature of the N2 in IrN2 crystal. Lattice parameters, bulk modulus, and the electronic structure of IrN2 under high pressure have also been investigated based on DFT. The compressibility along three cell vectors is very close to each other. The band gap increases a little with the pressure even when the pressure is up to 100 Gpa. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
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27. Dimetalloendofullerene U2@C60 Has a U--U Multiple Bond Consisting of Sixfold One-Electron-Two-Center Bonds.
- Author
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Xin Wu and Xin Lu
- Subjects
- *
FULLERENES , *METALS , *CHEMICAL bonds , *ELECTRONIC structure , *FERROMAGNETISM , *ATOMIC orbitals , *ENERGY-band theory of solids - Abstract
Endohedral metallofullerenes (EMFs) have been extensively studied since their discovery in 1985. Metal-metal bonds, nevertheless, have never been explicitly observed in EMFs synthesized so far. In this contribution, we show by means of all-electron relativistic density functional computations that the dimetalloendofullerene, U2@C60, has an unprecedented U-U multiple bond consisting solely of sixfold ferromagnetically coupled one-electron-two-center bonds with the electronic configuration (5fπu)²(5fσg)1- (5fδg)²(5fΦu)¹, which are dominated by the uranium 5f atomic orbitals. This bonding scheme is completely distinct from the metal-metal bonds discovered thus far in the d- and f-block polynuclear metal complexes. This finding initiates a connection of the metal-metal multiple bonding chemistry and the fullerene chemistry. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
28. Unprecedented 4-C26-Anion in Sc4C2C80.
- Author
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Kai Tan, Xin Lu, and Chun-Ru Wang
- Subjects
- *
ELECTRONIC structure , *SCISSION (Chemistry) , *CHEMICAL reactions , *CHEMICAL decomposition - Abstract
Metal carbide compound containing highly charged C2q-(q 5, 6) moiety is rather scarce. We show by means of density functional calculations that an unprecedented 4-C26-anion can viably exist as an endohedral Sc4C26cluster in the endofullerene Sc4C2C80. The electronic structure, ionization energy, electron affinity, 13C NMR chemical shifts, vibrational frequencies, and electrochemical redox potentials of this unique endofullerene have been predicted to assist future experimental characterization. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
29. Electronic Structure and Redox Properties of the Open-Shell Metal−Carbide Endofullerene Sc3C2@C80: A Density Functional Theory Investigation.
- Author
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Kai Tan and Xin Lu
- Subjects
- *
ELECTRONIC structure , *DENSITY functionals , *ATOMIC structure , *ENERGY-band theory of solids - Abstract
Density functional theory calculations have shown that the open-shell metal−carbide endofullerene Sc3C2@C80 has the valence state (Sc3+)3(C2)3-@C806-. A lot of low-lying isomers differing in geometries and locations of the endohedral [(Sc3+)3(C2)3-] cluster have been located, indicating unusual dual intramolecular dynamic behaviors of this endofullerene at room temperature. The electrochemical redox properties of this endofullerene have been elucidated in terms of electronic structure theory. Its redox states are found to follow the general charge−state formula (Sc3+)3C2(3-q)-@C806- (q is the charge of the whole molecule ranging from +1 to −3), demonstrating the high charge flexibility of the endohedral metal−carbide cluster. The structure of the endohedral [(Sc3+)3C2(3-q)-] cluster varies with the redox processes, shifting from a planar structure (for q = 0 and −1) to a trifoliate structure (for q = +1, −2, −3). [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
30. Spacing-driven collapse of band gap and magnetic order in Sr3Ir2O7.
- Author
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Guo, Chang-Min, Zhang, Hong, and Cheng, Xin-Lu
- Subjects
- *
BAND gaps , *MAGNETIC transitions , *FERMI surfaces , *METAL-insulator transitions , *BRILLOUIN zones , *ANTIFERROMAGNETISM , *TRANSITION metals - Abstract
Using first-principles methods, we investigated the effect of structural deformation on the electronic and magnetic properties of Sr 3 Ir 2 O 7 by two tuning ways: reducing only the interlayer spacing and the uniaxial-like compression. In both cases, an insulator-metal transition is successfully achieved with significantly different Fermi surface features. The former consists of a hole pocket and an electronic pocket, while for the latter, a pseudo-gap is captured near the center of the crystallographic Brillouin zone. The anti-ferromagnetism collapses completely and is not fully synchronized with the closing of the Mott gap in two kinds of compression cases, indicating that the conventional correlation between magnetic order and Mott insulating state does not exist here. Our research is conducive to understand the nature of lattice distortion-induced electronic and magnetic transitions, and will be expected to provide a new theoretical reference for the experimental regulation of novel metallic properties in iridium. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. Influences of neutral oxygen vacancies and centers on α-quartz.
- Author
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Li Hui-Ran, Cheng Xin-Lu, Zhang Hong, and Zhao Feng
- Subjects
- *
QUARTZ , *REFRIGERANTS , *OXYGEN , *ELECTRONIC structure , *DENSITY of states - Abstract
Our calculations demonstrate that the concentration of neutral oxygen vacancies can affect the geometrical structrue, electronic structure, and optical properties of α-quartz. Moreover, the distribution of the neutral oxygen divacancy can also exert some influence on the properties of α-quartz. The dissimilarity and similarities are presented in the corresponding density of state (DOS) and absorption spectrum. In addition, when a higher defect concentration is involved in α-quartz, the influence of center on the geometry of α-quartz becomes more significant. However, the introduction of an center barely results in any improvement compared with the influence produced by the corresponding neutral defect. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
32. First-principles study of structural, electronic and optical properties of ZnF2.
- Author
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Jian-Bang Wu, Xin-Lu Cheng, Hong Zhang, and Zheng-Wei Xiong
- Subjects
- *
MOLECULAR structure of zinc compounds , *OPTICAL properties of metals , *ELECTRONIC structure , *AB-initio calculations , *DENSITY functional theory - Abstract
The structural, electronic, and optical properties of rutile—, CaCl2−, and PdF2—ZnF2 are calculated by the plane-wave pseudopotential method within the density functional theory. The calculated equilibrium lattice constants are in reasonable agreement with the available experimental and other calculated results. The band structures show that the rutile—, CaCl2−, and PdF2—ZnF2 are all direct band insulator. The band gaps are 3.63, 3.62, and 3.36 eV, respectively. The contribution of the different bands was analyzed by the density of states. The Mulliken population analysis is performed. A mixture of covalent and weak ionic chemical bonding exists in ZnF2. Furthermore, in order to understand the optical properties of ZnF2, the dielectric function, absorption coefficient, refractive index, electronic energy loss spectroscopy, and optical reflectivity are also performed in the energy range from 0 to 30 eV. It is found that the main absorption parts locate in the UV region for ZnF2. This is the first quantitative theoretical prediction of the electronic and optical properties of ZnF2 compound, and it still awaits experimental confirmation. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
33. Different magnetic responses induced by unequal oxygen vacancies in SrIrO3.
- Author
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Guo, Chang-Min, Zhang, Hong, and Cheng, Xin-Lu
- Subjects
- *
METAL-insulator transitions , *MAGNETIC moments , *MAGNETIC properties , *OXYGEN - Abstract
Using first-principles calculations, we investigate the effects of two kinds of oxygen defects on the electronic and magnetic properties in SrIrO 3 bulk. One is the oxygen defect in IrO 2 plane (Ov1) and the other out-of-plane (Ov2). The results show that both oxygen defects enhance the inherent metallicity of the crystal and there is no tendency to achieve the Mott transition. Most surprised, we find that a small out-of-plane magnetic moment along c axis is formed due to the apical tilting of the defective octahedrons induced by the in-plane oxygen defects. While a local and weak ab in-plane ferromagnetic response comes from the out-of-plane defect which destroys the connectivity between adjacent layers and promotes a small in-plane rotation. In addition to the distortion of the defective blocks, the weak ferromagnetic phenomenon is also limited by the concentration of oxygen defects. Our research indicates that non-equivalent oxygen deficiencies exert distinct regulatory roles on the magnetic properties. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
34. Single-layer group IV-V and group V-IV-III-VI semiconductors: Structural stability, electronic structures, optical properties, and photocatalysis.
- Author
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Jia-He Lin, Hong Zhang, Xin-Lu Cheng, and Yoshiyuki Miyamoto
- Subjects
- *
PHOTOCATALYSIS , *SEMICONDUCTORS , *ELECTRONIC structure - Abstract
Recently, single-layer group III monochalcogenides have attracted both theoretical and experimental interest at their potential applications in photonic devices, electronic devices, and solar energy conversion. Excited by this, we theoretically design two kinds of highly stable single-layer group IV-V (IV=Si,Ge, and Sn; V=N and P) and group V-IV-III-VI (IV=Si,Ge, and Sn; V=N and P; III=Al,Ga, and In; VI=O and S) compounds with the same structures with single-layer group III monochalcogenides via first-principles simulations. By using accurate hybrid functional and quasiparticle methods, we show the single-layer group IV-V and group V-IV-III-VI are indirect bandgap semiconductors with their bandgaps and band edge positions conforming to the criteria of photocatalysts for water splitting. By applying a biaxial strain on single-layer group IV-V, single-layer group IV nitrides show a potential on mechanical sensors due to their bandgaps showing an almost linear response for strain. Furthermore, our calculations show that both single-layer group IV-V and group V-IV-III-VI have absorption from the visible light region to far-ultraviolet region, especially for single-layer SiN-AlO and SnN-InO, which have strong absorption in the visible light region, resulting in excellent potential for solar energy conversion and visible light photocatalytic water splitting. Our research provides valuable insight for finding more potential functional two-dimensional semiconductors applied in optoelectronics, solar energy conversion, and photocatalytic water splitting. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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