高压下超导体YBa2Cu3O7弹性性质的第一性原理研究

通过从头算密度泛函理论研究了YBa2Cu3O7的结构和弹性性质。发现c轴最容易压缩。另外,我们还计算了各种弹性性质与压强的关系,例如弹性模量,剪切模量,杨氏模量,泊松比。最后,我们获得了不同压强下的德拜温度和声速。     

金红石结构TiO2结构和热力学性质的第一性原理研究

利用基于密度泛函理论的第一性原理计算方法以及准谐德拜模型研究了金红石TiO2的结构和热力学性质。常温常压下所计算的晶格常数、体弹模量及其对压强的一阶导数与实验值和其他理论计算结果相符的较好。另外,我们还计算了体弹模量、热膨胀系数、热容与温度和压强的关系。     

First-principles calculations for electronic and optical properties of the zinc-blende structured BeS compound under pressure

The electronic and the optical properties of the cubic zinc-blende (ZB) BeS under high pressure have been investigated by using \it ab initio plane-wave pseudopotential density functional theory method in the generalised gradient approximation (GGA) for exchange-correlation interaction. The electronic band structure and the pressure dependence of the total and partial densities of state under pressure are successfully described. Our calculations show that the ZB BeS has large and indirect band gaps associated with (Γ → X) transitions in ambient conditions. The results obtained are consistent with the experimental data available and other calculations. The optical properties, including dielectric function, energy-loss function, complex refractive index, reflection and absorption spectra, are investigated and analysed at different external pressures. The results suggest that the optical absorption appears mostly in the ultra-violet region and the curve of refractive index shift toward high energies (blue shift) with pressure increasing.     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质.计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好.基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性.从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合.同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况.     

高温下季戊四醇晶体的结构和振动性质的分子动力学模拟

通过分子动力学研究了季戊四醇晶体在温度高达500K范围内的结构和振动性质。考察了季戊四醇晶体的晶格参数和分子构型等随温度变化情况,相对晶格常数a来说,晶格常数c容易被压缩。发现C-C,C-H和 C-O键随温度的变化较大,这意味着在分解过程中这些键可能较敏感,即最先断裂可能性较大。研究了季戊四醇晶体在不同温度下的振动,在常压下,我们所计算的振动频率高于实验结果,另外,我们还讨论了由温度引起的频率漂移。     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质。计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好。基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性。从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa 出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合。同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况。     

高温下季戊四醇晶体的结构和振动性质的分子动力学模拟(英文)

通过分子动力学研究了季戊四醇晶体在温度高达500K范围内的结构和振动性质.考察了季戊四醇晶体的晶格参数和分子构型等随温度变化情况,相对晶格常数a来说,晶格常数c容易被压缩.发现C-C,C-H和C-O键随温度的变化较大,这意味着在分解过程中这些键可能较敏感,即最先断裂可能性较大.研究了季戊四醇晶体在不同温度下的振动,发现大部分频率随温度的升高而降低.     

First-principles investigations on elastic and thermodynamic properties of zinc-blende structure BeS

In this paper the elastic and thermodynamic properties of the cubic zinc-blende structure BeS at different pressures and temperatures are investigated by using \textit{ab initio} plane-wave pseudopotential density functional theory method within the generalized gradient approximation (GGA). The calculated results are in excellent agreement with the available experimental data and other theoretical results. It is found that the zinc-blende structure BeS should be unstable above 60GPa. The thermodynamic properties of the zinc-blende structure BeS are predicted by using the quasi-harmonic Debye model. The pressure-volume-temperature ($P-V-T$) relationship, the variations of the thermal expansion coefficient $\alpha$ and the heat capacity $C_{V}$ with pressure $P$ and temperature $T$, as well as the Gr\"{u}neisen parameter-pressure-temperature ($\gamma -P-T$) relationship are obtained systematically in the ranges of 0--90GPa and 0--2000K.     

Electronic and optical properties of the zinc-blende structured LiZnN under pressure

The electronic and optical properties of the cubic zinc-blende (ZB) structured filled tetrahedral semiconductor α-LiZnN under pressure are investigated by using \textit{ab initio} plane wave pseudopotential density functional theory method within the generalized gradient approximation (GGA). The electronic band structure and the density of state under pressure are systematically described. The basic optical constants, including the reflection and absorption spectra, the energy-loss function, the complex refractive index and the dielectric function, are calculated and analysed at different external pressures. Our results suggested that the ZB α-LiZnN is transparent in the partially ultra-violet to the visible light region, and it seems that the transparency is hardly affected by the pressure.     

金电极下二元化合物氮化镓链结构演化和电导的从头计算

基于从头密度泛函理论结合非平衡格林函数方法，首次研究了二元化合物GaN链介于两个金电极之间的电子输运性质。模拟了Au-(GaN)2-Au节点断裂过程，计算了相应的结合能，获得了平衡态电导以及平衡态下节点的投影态密度。此外，计算了平衡态下节点在微小偏压下的电流和电导。结果发现，随着偏压增强，GaN分子链的电导也随之下降。最后给出的伏安特性曲线呈现一个非线性关系，表明节点具有类似半导体的特征。