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electronic structure and optical properties of LiXH_3 and XLiH_3 (X = Be, B or C)

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Chinese Physics B 2008年第6期17卷 2222-2228页

作者：伞晓娇何志马琰铭崔田刘冰冰邹广田 National Laboratory of Superhard Materials Jilin University

The equilibrium lattice constant, the cohesive energy and the electronic properties of light metal hydrides LiXH3 and XLiH3 （X = Be, B or C） with perovskite lattice structures have been investigated by using the pseudopotential plane-wave method. Large energy gap of LiBeH3 indicates that it is insulating, but other investigated hydrides are metallic. The pressure-induced metallization of LiBeH3 is found at about 120 GPa, which is attributed to the increase of Be-p electrons with pressure. The electronegativity of the p electrons of X atom is responsible for the metallicity of the investigated LiXH3 hydrides, but the electronegativity of the s electrons of X atom plays an important role in the metallicity of the investigated XLiH3 hydrides. In order to deeply understand the investigated hydrides, their optical properties have also been investigated. The optical absorption of either LiBeH3 or BeLiH3 has a strong peak at about 5 eV, showing that their optical responses are qualitatively similar. It is also found that the optical responses of other investigated hydrides are stronger than those of LiBeH3 and BeLiH3 in lower energy ranges, especially in the case of CLiH3.

关键词： plane-wave method metal hydrides electronic structure optical properties

electronic structure and optical properties of plutonium dioxide from first-principles calculations

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Rare Metals 2016年第8期35卷 643-648页

作者： Jun Chen Da-qiao Meng Qiu-Yun Chen Wen-Hua Luo Science and Technology on Surface Physics and Chemistry Laboratory Mianyang 621907China

The electronic structure and optical properties of plutonium dioxide were calculated using the generalized gradient approximation with a Hubbard parameter U （GGA ＋ U） for considering the strong coulomb correlation between localized Pu of electrons based on the first-principles density functional theory. The calculated results show that PuO2 is a semiconductor material with the band gap of 1.8 eV, which is in good agreement with the corresponding experimental data. Furthermore, the dielectric function, reflectivity, refractive index, and extinction coefficient were calculated and analyzed using the Kramers-Kronig relationship for PuO2. The calculated results were compared with the experimental data from the published literature.

关键词： PuO2 Generalized gradientapproximation + U electronic structure Optical properties

electronic structure and mechanical properties of layered compound YB_2C_2:A promising precursor for making two dimensional(2D) B_2C_2 nets

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Journal of Materials Science & Technology 2017年第9期33卷 1044-1054页

作者： Yanchun Zhou Huimin Xiang Xiaohui Wang Wei Sun Fu-Zhi Dai Zhihai Feng Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp anisotropic chemical bonding and properties becomes emergent. In this work, the stability, electronic structure, elastic properties, and lattice dynamics of YBCwere investigated. Strong anisotropy in elastic properties is revealed, i.e., high Young’s modulus in a-b plane but low Young’s modulus in c direction. The maximum to minimum Young’s modulus ratio is 2.41 and 2.45 for YBCwith P42/mmc and P4/mbm symmetry, respectively. The most likely systems for shear sliding or microdelaminating are(001)[100] and(001)[010]. The anisotropic elastic properties are underpinned by the anisotropic chemical bonding, i.e., strong bonding within the BCnets and weak bonding between Y atom layers and BCnets. YBCis electrically conductive and the contributions to the electrical conductivity are from delocalized Y 4deas well as Bpandpzelectrons. The layered crystal structure, sharp anisotropic mechanical properties, and metallic conductivity endorse YBCpromising as a precursor for new 2D BCnets.

关键词： YB2C2 Layered compounds electronic structure Mechanical properties 2D graphite like materials

electronic structure and Magnetic Properties of Rh_(13) Cluster with Three Possible Symmetries

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Chinese Journal of Structural Chemistry 2006年第6期25卷 667-672页

作者： KUANG Xiang-Jun School of Science Southwest University of Science and Technology Mianyang Sichuan 621010 China

electronic and magnetic properties of 13-atom Rh clusters with three possible high symmetry geometries have been studied by using the first-principles DV-LSD method. An anomalous symmetry dependence of the cluster magnetism was found that the total magnetic moment of the icosahedral Rh13 cluster is smaller than that of the other two lower-symmetry clusters in a wide range of interatomic spacings. An energy difference is identified to explain this anomalous relationship, which has been found to be also useful for judging whether the broadening technique is correctly used and whether multiple input potentials must be used to reach the actual ground state in the LSD calculations. The calculated results are compared and discussed with those of previous theory and recent experiment. The actual geometry of the Rh13 cluster is suggested to be a distorted icosahedron.

关键词： Rh13 clusters electronic structure magnetic properties three possible symmetries

electronic structure and optical properties of Mg_xZn_(1-x)S bulk crystal using first-principles calculations

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Chinese Physics B 2014年第10期23卷 441-446页

作者：余志强徐智谋武兴会 Wuhan National Laboratory for Optoelectronics School of Optical and Electronic InformationHuazhong University of Science and Technology

We perform the first-principles calculations within the framework of density functional theory to determine the elec- tronic structure and optical properties of MgxZnl-xS bulk crystal. The results indicate that the electronic structure and optical properties of MgxZnl_xS bulk crystal are sensitive to the Mg impurity composition. In particular, the MgxZnl-xS bulk crystal displays a direct band structure and the band gap increases from 2.05 eV to 2.91 eV with Mg dopant compo- sition value x increasing from 0 to 0.024. The S 3p electrons dominate the top of valence band, while the Zn 4s electrons and Zn 3p electrons occupy the bottom of conduction band in MgxZnl_xS bulk crystal. Moreover, the dielectric constant decreases and the optical absorption peak obviously has a blue shift. The calculated results provide important theoretical guidance for the applications of MgxZn1-xS bulk crystal in optical detectors.

关键词： first-principles MgxZn1-xS electronic structure optical properties

electronic structure and thermodynamic properties of LiBC under high pressure

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Chinese Physics B 2008年第7期17卷 2639-2645页

作者：艾琼付志坚程艳陈向荣 Institute of Atomic and Molecular Physics Sichuan University College of Physical Science and Technology Sichuan University International Centre for Materials Physics Chinese Academy of Sciences

This paper investigates the electronic structure and thermodynamic properties of LiBC in the hexagonal structure by using the generalized gradient approximation （GGA） and local density approximation correction scheme in the frame of density functional theory. The geometric structure of LiBC under zero pressure, and the dependences of the normalized lattice parameters a/ao and c/co, the ratio e/a, the normalized primitive volume V/Vo on pressure are given. The thermodynamic quantity （including the heat capacity Cv, Debye temperature 6~D, thermal expansion a and Grfineisen parameter -y） dependences on temperature and pressure are obtained through the GGA method and the quasi-harmonic Debye model. The band structures and density of state of LiBC under different pressures have also been analysed.

关键词： thermodynamic properties electronic structure density functional theory LiBC

electronic structure evolution accompanying heavy fermion formation in CeCu2Si2

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Science China(Physics,Mechanics & Astronomy) 2020年第8期63卷 123-131页

作者： XueBing Luo Yun Zhang QiuYun Chen Qin Liu LiZhu Luo ShiYong Tan XieGang Zhu XinChun Lai Science and Technology on Surface Physics and Chemistry Laboratory Mianyang 621908China

The cooper pairs in the heavy-fermion superconductor CeCu2Si2 are formed of heavy ***,the heavy fermions are fundamental to the emergence of unconventional superconductivity and associated non-Fermi-liquid behavior in the normal *** interplay between localization and itinerancy manifested on the electronic structure is key for understanding the heavyfermion ***,via the first-principle density functional theory(DFT)combined with single-site dynamical mean-field theory(DMFT),we investigate the temperature(T)evolution of the electronic structure of CeCu2Si2 in the normal state,focusing on the role of the 4f states in the low energy *** characteristic temperature scales of this evolution,which accompanied the heavy-fermion formation,are *** coherence onset temperature is around 130K,whereas the heavy-fermion band formation temperature is between 40 and 80K;both characteristic temperature scales are higher than the transport coherence ***,the heavy-fermion formation is confirmed by calculating its effective mass variation with the *** on the calculated T-dependent evolution of the 4 f orbital occupancy and electronic structure,an explanation on the behavior of the temperature evolution of the correlation strength of CeCu2Si2 is *** results offer a comprehensive microscopic picture of the heavy-fermion formation in CeCu2Si2,which is essential for further understanding the emergent superconducting pairing mechanism.

关键词： CeCu2Si2 heavy-fermion formation temperature electronic structure DFT+DMFT

electronic structure and optical properties of Al and Mg co-doped GaN

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Chinese Physics B 2013年第11期22卷 490-495页

作者：纪延俊杜玉杰王美山 Department of Physical and electronic Science Bingzhou Univercity School of Physics and Optoelectronic Engineering Ludong University

The electronic structure and optical properties of A1 and Mg co-doped GaN are calculated from first principles using density function theory with the plane-wave ultrasoft pseudopotentiai method. The results show that the optimal form of p-type GaN is obtained with an appropriate AI：Mg co-doping ratio rather than with only Mg doping. A1 doping weakens the interaction between Ga and N, resulting in the Ga 4s states moving to a high energy region and the system band gap widening. The optical properties of the co-doped system are calculated and compared with those of undoped GaN. The dielectric function of the co-doped system is anisotropic in the low energy region. The static refractive index and reflectivity increase, and absorption coefficient decreases. This provides the theoretical foundation for the design and application of A1-Mg co-doped GaN photoelectric materials.

关键词： GaN first-principles electronic structure optical properties

electronic structure of O-doped SiGe calculated by DFT+U method

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Chinese Physics B 2016年第12期25卷 377-389页

作者：赵宗彦杨雯杨培志 Faculty of Materials Science and Engineering Kunming University of Science and Technology Yunnan Key Laboratory of Micro/Nano Materials & Technology School of Materials Science and EngineeringYunnan University Key Laboratory of Advanced Technique & Preparation for Renewable Energy Materials (Ministry of Education) Yunnan Normal University

To more in depth understand the doping effects of oxygen on SiGe alloys, both the micro-structure and properties of O-doped SiGe （including： bulk, （001） surface, and （110） surface） are calculated by DPT ＋ U method in the present work. The calculated results are as follows. （i） The （110） surface is the main exposing surface of SiGe, in which O impurity prefers to occupy the surface vacancy sites. （ii） For O interstitial doping on SiGe （110） surface, the existences of energy states caused by 0 doping in the band gap not only enhance the infrared light absorption, but also improve the behaviors of photo-generated carriers. （iii） The finding about decreased surface work function of O-doped SiGe （110） surface can confirm previous experimental observations. （iv） In all cases, O doing mainly induces the electronic structures near the band gap to vary, but is not directly involved in these variations. Therefore, these findings in the present work not only can provide further explanation and analysis for the corresponding underlying mechanism for some of the experimental findings reported in the literature, but also conduce to the development of μc-SiGe-based solar ceils in the future.

关键词： SiGe alloys 0 doping electronic structure density functional theory (DFT) calculations