Li-Y-H三元氢化物的结构和稳定性研究

本文基于粒子群优化算法的结构预测方法结合第一性原理计算,研究了LiYH₄,Li₂YH₅和Li₃YH₆在0—300 GPa压力范围内的晶体结构、电子结构、热力学和动力学稳定性.研究结果表明LiYH₄-P4/nmm,Li₂YH₅-I4/mmm和Li₃YH₆-P4/nmm结构可分别在169—221 GPa,141—300 GPa和166—300 GPa压力范围内由LiH和YH₃按一定配比加压合成.富氢化合物的超导电性研究成为近年来高温超导体研究领域的热点,该研究结果有希望为Li-Y-H三元体系氢化物的超导电性研究及实验合成提供数据支撑.     

基于拼接的大视场虚拟现实头戴显示装置

虚拟现实技术是头戴显示技术的一个重要分支。为了提高虚拟现实头戴显示装置的视场角,获得更高的沉浸感,设计了一种基于视场拼接原理的大视场虚拟现实头戴显示装置。利用4套横向视场角为80°,且完全相同的目视光学系统,通过拼接实现大视场虚拟现实头戴显示。本装置的双目横向视场角为162°,其中每个单目系统的横向视场角为126°,双目重叠视场角为90°。     

Pu-H2体系从头算分子动力学的研究

本文应用Gaussian09程序,通过密度泛函理论的相关方法,对钚-氢气体系进行了计算和分析。计算得到了钚与氢气的沿势能剖面的各个特殊点的几何结构。通过约化密度梯度分析方法分析了反应路径中的所有特殊结构的化学键的性质。通过从头算分子动力学的计算,由直接经典轨迹的计算结果得到了反应体系的几何结构、能量随时间的变化,并分析得到体系的大部分能量转化为反应产物的振动能。     

Elastic,vibrational, and thermodynamic properties of Sr_(10)(PO_4)_6F_2 and Ca_(10)(PO_4)_6F_2 from first principles

The electronic, elastic, vibrational, and thermodynamic properties of Sr_(10)(PO_4)_6F_2(Sr-FAP) and Ca_(10)(PO_4)_6F_2(CaFAP) are systematically investigated by the first-principles calculations. The calculated electronic band structure indicates that the Sr-FAP and Ca-FAP are insulator materials with the indirect band gap of 5.273 eV and 5.592 eV, respectively. The elastic constants are obtained by the "stress–strain" method, and elastic modulus are further evaluated and discussed. The vibrational properties, including the phonon dispersion curves, the phonon density of states, the Born effective charge, and associated longitudinal optical and transverse optical(LO–TO) splitting of optical modes, as well as the phonon frequencies at zone-center are obtained within the linear-response approach. Substitution of Ca by Sr causes phonon frequencies to shift to lower values as expected due to the mass effect. Additionally, some phonon-related thermodynamic properties, such as Helmholtz free energy F, internal energy E, entropy S, and specific heat C_V of Sr-FAP and Ca-FAP are predicted with the harmonic approximation. The present calculated results of two apatites are consistent with the reported experimental and theoretical results.     

UO2分子的多体项展式势能函数

采用Ｇａｕｓｓｉａｎ９４ Ｗ 程序和相对论有效原子实理论模型优化出ＵＯ２ 分子稳定构型为线性Ｏ—Ｕ—Ｏ（ Ｄ∞ｈ） ,亚稳定构型为Ｕ—Ｏ—Ｏ（ Ｃ∞ｖ） ,计算出平衡核间距和振动频率．然后根据微观可逆性原则,准确地判断了ＵＯ２ 分子的离解极限．运用多体项展式理论方法,导出了基态ＵＯ２ 分子的分析势能函数,绘出其势能面等值图,准确地展现了Ｏ—Ｕ—Ｏ（ Ｄ∞ｈ） 稳定结构和Ｕ—Ｏ—Ｏ（ Ｃ∞ｖ） 亚稳定结构,根据势能面等值图讨论了Ｏ（３Ｐｇ） ＋ ＵＯ 反应和Ｕ＋ Ｏ２（ Ｘ３Σ－ｇ ） 反应的势能面静态特征     

The splitting of low-lying or low excited states for hydride molecules （cations） of the third period under spin-orbit coupling

This paper reports that the splitting of potential energy curves for the low-lying or low excited states for hydride molecules （cations） （MgH, AlH^＋, SiH, PH^＋, SH,ClH^＋） of the third period under Spin-Orbit Coupling has been calculated by using the Spin-Orbit Multi-Configuration Quasi-Degenerate Perturbation Theory （SO-MCQDPT） method. Then, spectroscopic constants of the split states have been derived from the Murrell-Sorbie function. The calculated dissociation energies for the spectrum branch terms have been given, respectively. The spectroscopic constants and dissociation energies for the spectrum branch terms are given for the first time in this paper.     

Structural,electronic,vibrational,and thermodynamic properties of Zr_(1-x)Hf_xCo:A first-principles-based study

The physical properties including structural,electronic,vibrational and thermodynamic properties of Zr1-xHfx Co(x is the concentration of constituent element Hf,and changes from 0 to 1) are investigated in terms of the ABINIT program.The results reveal that all of Zr_(1-x)Hf_x Co have similar physical properties.When Hf concentration x gradually increases from 0.0 to 1.0,the lattice constant decreases from 3.217 ?A to 3.195 ?A very slowly.The calculated density of states(DOS)indicates that the metallic nature is enhanced and the electrical conductivity turns better with the increase of Hf.Moreover,as Hf concentration increases from 0 to 1,the Fermi energy gradually increases from-6.96 e V to-6.21 e V,and the electronic density of states at the Fermi level(N(E_f)) decreases from 2.795 electrons/e V f.u.down to 2.594 electrons/e V f.u.,both of which imply the decrease of chemical stability.The calculated vibrational properties show that the increase of Hf concentration from 0 to 1 causes the maximum vibrational frequency to decrease gradually from about 223 cm~(-1) to 186 cm~(-1),which suggests a lower dispersion gradient and lower phonon group velocities for these modes.Finally,the phonon related thermodynamic properties are obtained and discussed.     

N2分子X^1Σg^＋,A^3Σu^＋和B^3Пg的势能函数

用文献［１，２，８］介绍的方法推导了Ｎ２分子的基态（Ｘ＾１Σｇ＾＋）的激发态（Ａ＾３Σｕ＾＋和Ｂ＾３Пｇ）的合理离解极限。计算并比较了在６－３１１Ｇ＾＊基集合，ＵＨＦ、ＣＩＤ、ＵＣＩＳＤ和ＱＣＩＳＤ水平下Ｎ２分子上述三个电子态的平衡结构和谐振频率；并用ＱＣＩＳＤ／６－３１１Ｇ＾＊计算了各态的系列单点势能值，由正规方程组拟合Ｍｕｒｒｅｌｌ－Ｓｏｒｂｉｅ函数得到了相应各态的完整势能函数，结果与实验数计     

Y(Fe,M)12化合物的电子结构与磁性(M=Nb,Si)

采用新近发展的全势能线性缀加平面波((L)APW) 局域轨道(lo)和广义梯度近似(GGA)密度泛函方法计算了Y(Fe,M)12化合物(M=Nb,Si)的电子结构,得到了相应的总态密度和局域态密度,并分析了替代原子与替代晶位不同引起态密度的变化。根据计算结果预测的居里温度变化与实验结果基本一致。     

PdH2、YH2分子的结构与势能函数

用密度泛函理论的B3LYP方法,对钯和钇原子采用SDD收缩价基函数,氢原子采用6-311＋＋G**全电子基函数,对PdH2和YH2体系的结构进行优化计算,得到PdH2分子最稳态为C2v构型,电子组态为1A1,平衡核间距RPdH=0.1692 nm,键角∠HPdH=29.4°,离解能De=5.5212 eV,基态简正振动频率:ν1(b2)=1470.1 cm－1、ν2(a1)=1007.9 cm－1、ν3(a1)=2907.0 cm－1.YH2分子最稳态也为C2v构型,电子组态2A1,RYH=0.1962 nm,∠HYH=114.3°,De=5.6691 eV,基态简正振动频率:ν1(b2)=1457.9 cm－1、ν2(a1)=476.0 cm－1、ν3(a1)=1506.3 cm－1.由微观过程的可逆性原理分析了分子的可能离解极限.并用多体项展式理论方法分别导出基态PdH2和YH2分子的势能函数,其等值势能面图准确地再现了PdH2和YH2分子的结构特征和离解能,由此讨论了Pd ＋ H2和Y ＋ H2分子反应的势能面静态特征.