First-principles study of electronic structure, chemical bonding, and optical properties of cubic SrHfO3

Electronic structure and optical properties of SrHfO₃ are calculated using the full potential linearized augmented plane wave plus local orbitals method. The calculated equilibrium lattice is in reasonable agreement with the experimental data. From the density of states (DOS) as well as charge density studies, we find that the bonding between Sr and HfO₃ is mainly ionic and that HfO₃ entities bond covalently. The complex dielectric functions are calculated, which are in good agreement with the available experimental results. The effect of the spin-orbit coupling on the optical properties is also investigated and found to be quite small.     

Structural,electronic, optical and bonding properties of strontianite,SrCO3: First-principles calculations

The first-principles calculations are performed within the density functional theory to investigate the crystal structure, energy band structure, density of states, optical properties, and bonding properties of strontianite. The optimized structure parameters and bonding results with the generalized gradient approximation (GGA) functional and the localized density approximation (LDA) functional are in good agreement with the earlier experimental data. The band structure, density of states and chemical bonding of strontianite have been calculated and analyzed. The indirect band gap of strontianite is estimated to be ~4.45 eV (GGA) or ~4.24 eV (LDA). The absorption, reflectivity, refractive index and extinction coefficient have been calculated using the imaginary part of the dielectric function. The calculated results of the optical properties show that strontianite has an optical anisotropy along [100] (or [010]) and [010] polarization directions of incoming light. Furthermore, the calculated results of the density of states and Mulliken population indicate that the interactions among atoms are both ionic and covalent bonding in strontianite.     

First-principles study of structural and electronic properties of Cd3P2

First-principles linear combination of atomic orbitals method within the framework of density functional theory is applied to study structural and electronic properties of tetragonal and cubic phases of Cd₃P₂. The equilibrium lattice constants and bulk moduli deduced from Murnaghan equation of state for the two structures are in good agreement with the experiment. Enthalpy–pressure curves do not show possibility of pressure induced structural phase transitions between the two structures up to 80 GPa. Electronic band structures and Mulliken population analysis for the two structures are presented. It is found that tetragonal Cd₃P₂ has direct band gap 1.38 eV while cubic structure shows indirect band gap of 0.35 eV. The branch point energies for the tetragonal structure lie below the conduction band while for cubic structure it lies in the conduction band. Mulliken population analysis shows that occupancies in 5sp, 6sp and 5d states of Cd and 3sp and 4sp states of P are largely affected on bond formation.     

First-principles investigation of structural,mechanical, electronic,and bonding properties of NaZnSb

The structural, mechanical, electronic, and bonding properties and phase transition of NaZnSb are explored using the generalized gradient approximation based on ab initio plane-wave pseudopotential density functional theory. With the help of the quasi-harmonic Debye model, we probe the Grüneisen parameter, thermal expansivity, heat capacity, Debye temperature, and entropy of NaZnSb in the tetragonal phase. The results indicate that the lattice constants and the bulk modulus and its first pressure derivative agree well with the available theoretical and experimental data. NaZnSb in its ground state structure exhibits a distinct energy gap of about 0.41 eV, which increases with increasing pressure. Our conclusions are consistent with the theoretical predictions obtained by the ABINIT package, but are different from those obtained through the tight-binding linear muffin-tin orbital method. As a result, further experimental and theoretical researches need to be carried out. For the purpose of providing a comparative and complementary study for future research, we first investigate the thermodynamic properties of NaZnSb.     

First-principles study of structural,electronic, and optical properties of ZnSnO3

The structural, electronic, and optical properties of ZnSnO₃ were investigated using density functional theory within the generalized gradient approximation. The structure parameters obtained agree well with the experimental results. The electronic structures indicate that ZnSnO₃ is a semiconductor with a direct band gap of 1.0 eV. The calculated optical spectra can be assigned to contributions of the interband transitions from valence band O 2p levels to conduction band Sn 5s levels or higher conduction band Zn 3d levels in the low-energy region, and from O 2p to Sn 5p or Zn 4p conduction band in the high-energy region.     

First-principles study of structural,electronic and optical properties of ZnF_2

The structural, electronic, and optical properties of rutile-, CaC12-, 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.     

First-principles study of structural, mechanical, electronic and optical properties of 3R- and 2H-CuGaO2

We calculated the structural parameters, elastic, mechanical, electronic and optical properties of 3R- and 2H-CuGaO₂ using the first-principles density-functional theory. The results show that the structural parameters of two phases are in good agreement with previous theoretical and experimental data. Two phases are mechanically stable, behave in ductile manner and have indirect band gap. The analyses of electronic structures and charge densities of two phases show mainly covalent nature in Cu-O bonds and coexistence of both ionic and covalent nature in Ga-O bonds. The optical properties are obtained and discussed, including the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, energy-loss spectrum and complex conductivity function, which provide useful information for the future applications of CuGaO₂.     

First-principles study of structural,electronic and optical properties of orthorhombic SrZrO3

We have investigated the structural parameters, electronic structure and optical properties of orthorhombic SrZrO₃ using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT). Our calculated structural parameters are in good agreement with the previous theoretical and experimental data. Band structure, density of states and chemical bonding have been systematically studied. Furthermore, the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, loss function and optical conductivity are calculated, which show an optical anisotropy in the components of polarization directions (100), (010) and (001).     

First-principles study of the dielectric properties and infrared reflectance spectrum of Y2O3

Yttrium oxide is an important laser and infrared optical material. The structural, vibrational and dielectric properties of Y ₂O₃ are calculated from first principles using the plane-wave pseudopotential method. The dielectric permittivity tensors, infrared-active phonon frequencies at the Brillouin zone center and the LO/TO splitting are reported within the framework of density functional perturbation theory. Contributions to the static dielectric constant from each infrared-active mode are presented. It is shown that Y ₂O₃ has an electronic dielectric constant larger than that of the lattice contributions. Dielectric, refractive index, extinction coefficient and infrared reflectance spectra of Y ₂O₃ are given, and the figures suggest that Y ₂O₃ presents good transmission properties in the spectrum range above 800 cm^?1 or below 400 cm^?1.     

BaHfO3纳米薄膜电子结构、光学和弹性性质的第一性原理研究

采用基于密度泛函理论的第一性原理方法,在局域密度近似（LDA）下研究了厚度为0.626～2.711nm (100)面BaHfO3薄膜的电子结构、光学和弹性性质．电子结构和光学性质计算结果表明：以BaO为表面层原子的BaHfO3纳米薄膜均为直接带隙半导体材料,带隙随薄膜厚度减小而逐渐减小,表现出明显的量子尺寸效应,此时薄膜的光学吸收边发生红移,吸收带出现窄化现象．以HfO2作为表面层原子的BaHfO3薄膜则属于间接带隙半导体材料,且带隙随薄膜厚度减小而微弱增加．弹性性质计算结果表明：体弹模量、剪切模量和杨氏模量等表征材料硬度的力学参数均随BaHfO3纳米薄膜厚度减小而显著减小,呈现尺寸效应．电荷密度分布分析揭示了薄膜厚度改变了BaHfO3纳米薄膜的价健特性,这是材料硬度改变的内在原因．该研究结果为BaHfO3纳米薄膜材料的设计与应用提供了理论依据．     

First-principles study of structural,elastic, electronic and thermodynamic properties of topological insulator Bi2Se3 under pressure

The structural, elastic, electronic and thermodynamic properties of the rhombohedral topological insulator Bi₂Se₃ are investigated by the generalized gradient approximation (GGA) with the Wu–Cohen (WC) exchange-correlation functional. The calculated lattice constants agree well with the available experimental and other theoretical data. Our GGA calculations indicate that Bi₂Se₃ is a 3D topological insulator with a band gap of 0.287 eV, which are well consistent with the experimental value of 0.3 eV. The pressure dependence of the elastic constants C_ij, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson’s ratio σ of Bi₂Se₃ are also obtained successfully. The bulk modulus obtained from elastic constants is 53.5 GPa, which agrees well with the experimental value of 53 GPa. We also investigate the shear sound velocity V_S, longitudinal sound velocity V_L, and Debye temperature Θ_E from our elastic constants, as well as the thermodynamic properties from quasi-harmonic Debye model. We obtain that the heat capacity C_v and the thermal expansion coefficient α at 0 GPa and 300 K are 120.78 J mol^?1 K^?1 and 4.70 × 10^?5 K^?1, respectively.     

First-principles study on the electronic and optical properties of BiFeO3

The structural, electronic, and optical properties of multiferroic bismuth ferrite (BiFeO₃) are investigated using density functional theory within generalized gradient approximation (GGA). The calculated lattice parameters are in good agreement with the experimental data. The electronic structure shows that BiFeO₃ has an indirect (very close to direct) band gap of 1.06 eV. The complex dielectric function, absorption spectra, refractive index, extinction coefficient, energy-loss spectrum and reflectivity are calculated, and the results are compared with the available experimental data. Finally, the optical properties of BiFeO₃ are discussed based on the band structure calculations.     

First-principles study of structural,electronic,elastic,and thermal properties of Imm2-BC

Using the first-principles method, we predict an orthorhombic boron–carbon binary structure with sp~ace group Imm2.This structure is verified to be dynamically and mechanically stable, and possesses a cavity of 27.5 ~2 that makes it a potential molecular sieve material. The C sp~2 and sp~3 hybridized bonding in Imm2 BC is an important factor for its structural stability. The energy band calculations reveal that Imm2 BC is a semiconductor with a band gap of 1.3 eV and has a promising application in the electro-optic field. The lattice thermal conductivity along the crystal [100] direction at room temperature is 186 W·m~(-1)·K~(-1), that is about 5 times higher than those along the [010] and [001] directions, which stems from the different group velocity along the crystal direction. Moreover, the acoustic-optical coupling is important for heat transp~ort in Imm2 BC, and the contribution of optical phonons to lattice thermal conductivity in the [100], [010], and [001]directions is 49%, 59%, and 61%, resp~ectively. This study gives a fundamental understanding of the structural, electronic,elastic, and heat transp~ort properties in Imm2 BC, further enriching the family of boron–carbon binary compounds.     

BaZrO3和CaZrO3能带和光学性质的第一性原理研究

采用基于密度泛函理论基础上的CASTEP软件包,计算了BaZrO3和CaZrO3的能带以及光学性质.计算得到BaZrO3直接带隙和间接带隙分别为3.49 eV和3.23eV,CaZrO3直接带隙和间接带隙分别为3.73 eV和3.38 eV.对这两种材料的介电函数、吸收系数、反射系数、折射系数、湮灭系数和能量损失系数等光学系数进行了计算,并基于电子能带对光学性质进行了解释.得出,光学特性的异同是由于其内部微观结构上的异同所引起的.     

N掺杂SnO2材料光电性质的第一性原理研究

采用全电势线性缀加平面波(full potential linearized augmented plane wave method,简记为FP-LAPW)方法,基于密度泛函理论第一性原理计算分析N掺杂SnO₂材料,研究了在N替代O原子和N替代Sn原子情况下的电子态密度、电荷密度分布以及光学性质.研究表明N掺杂替代Sn较之N掺杂替代O原子的带隙要宽,都宽于SnO₂的本征带隙,且两种情况下N分别处于负氧化态和正氧化态,其介电函数谱也与带隙对应发生蓝移,从理论上指出     

First-principles study of electronic structure and magnetic properties of Sr3Fe2O5 oxide

We investigate the electronic structure and magnetic properties of layered compound Sr₃Fe₂O₅ based on first-principles calculations in the framework of density functional theory with GGA+U method. Under high pressure, the ladder-type layered structure of Sr₃Fe₂O₅ is transformed into the infinite layered structure accompanied by a transition from G-type anti-ferromagnetic (AFM) insulator to ferromagnetic (FM) metal and a spin transition from S=2 to S=1. We reproduce these transformations in our calculations and give a clear physical interpretation.     

First-principles study on linear and nonlinear optical properties of ZnGeP_2

The study of the linear and nonlinear optical properties of Zn Ge P2 based on density functional theory has been carried out. In order to get a more physical picture in the infrared region, terms which are considered as the phonon effect were added to the calculated refractive dispersion curves. The phonon-corrected calculation curves show excellent agreement with experimental refractive indexes, which gives a better comprehension of the linear optical proprieties in the transparent region. The static nonlinear optical susceptibility was investigated using approaches based on the sum over states and the2 n + 1 theorem methods. Both of the results of these two methods reasonably coincided with the experimental results.     

Si基外延Ru2Si3电子结构及光学性质研究

采用基于第一性原理的赝势平面波方法,对异质外延关系为Ru₂Si₃ （100）//Si（001）,取向关系为Ru₂Si₃［010］//Si［110］正交相的Ru₂Si₃平衡体系下的能带结构、态密度和光学性质等进行了理论计算.计算结果表明：当晶格常数a取值为1093 nm时,正交相Ru₂Si₃处于稳定状态并且是具有带隙值 关键词： 外延 第一性原理 电子结构 光学性质     

Band structure,Fermi surface,elastic,thermodynamic,and optical properties of AlZr_3,AlCu_3,and AlCu_2Zr:First-principles study

The electronic properties(Fermi surface,band structure,and density of states(DOS)) of Al-based alloys AlM_3(M=Zr and Cu) and AlCu_2Zr are investigated using the first-principles pseudopotential plane wave method within the generalized gradient approximation(GGA).The structural parameters and elastic constants are evaluated and compared with other available data.Also,the pressure dependences of mechanical properties of the compounds are studied.The temperature dependence of adiabatic bulk modulus,Debye temperature,specific heat,thermal expansion coefficient,entropy,and internal energy are all obtained for the first time through quasi-harmonic Debye model with phononic effects for T = 0 K-100 K.The parameters of optical properties(dielectric functions,refractive index,extinction coefficient,absorption spectrum,conductivity,energy-loss spectrum,and reflectivity) of the compounds are calculated and discussed for the first time.The reflectivities of the materials are quite high in the IR-visible-UV region up to ~ 15 eV,showing that they promise to be good coating materials to avoid solar heating.Some of the properties are also compared with those of the Al-based Ni_3 Al compound.     

Sb、Sm共掺杂SnO2的电子结构与光学性质第一性原理研究

采用基于密度泛函理论的第一性原理计算方法,构建了Sm、Sb及Sm和Sb共掺杂SnO₂超晶胞模型,研究了经过几何优化后的各掺杂体系的焓变值、能带结构、态密度、电荷布居、介电常数、吸收系数、反射率等光电性质.结果表明：Sm和Sb的掺杂可以有效地提升SnO₂的导电性能,且Sb和Sm共掺杂体系的电学性能最佳. Sm和Sb掺杂还可以增加SnO₂在红外波段的电子极化能力和电子跃迁概率,提升了红外反射率,且共掺杂体系的电子束缚能力最强、反射率最高.这为SnO₂基光电材料的研制提供了一定的理论依据.