Al的微观组态与LaNi3.75Al1.25的结构和弹性第一性原理研究

在全电子水平上，采用广义梯度近似密度泛函理论和全势能线性缀加平面波方法并结合二维立方拟合方法，对LaNi_3.75Al_1.25合金的晶体结构与弹性性质进行了理论研究.计算结果给出合金的晶格常数a=b=0.5137　nm，c=0.4018　nm，Al原子在晶胞中的微观分布为同时占据部分3g和2c等价格位，弹性常数C₁₁+C₁₂=281.2，C₁₃=82.3，C₃₃=227.3，以及体弹性模量B＝124.5、切变模量G＝68.2　GPa.还对态密度、能带结构和电荷密度进行了计算分析，并给出材料LaNi_3.75Al_1.25的电子线性比热系数23.45　mJ/molK². 关键词： 3.75Al_1.25')" href="#">LaNi_3.75Al_1.25 储氢合金 全势能线性缀加平面波 弹性常数     

金属有机物化学气相沉积法生长Ga2（1-x）In2xO3薄膜的结构及光电性能研究

采用金属有机物化学气相沉积（MOCVD）法在蓝宝石（0001）衬底上制备出了Ga_2（1-x）In_2xO₃（x=01—09）薄膜,研究了薄膜的结构、电学和光学特性以及退火处理对薄膜性质的影响.测量结果表明：当In组分x=02时,样品为单斜β-Ga₂O₃结构;x=05的样品,薄膜呈现非晶结构,退火处理后薄膜结构得到明显的改善 关键词： 金属有机物化学气相沉积 2（1-x）In_2xO₃薄膜')" href="#">Ga_2（1-x）In_2xO₃薄膜 蓝宝石衬底 退火     

La1-xSrxFeO3-δ（0≤x≤2/3）的低频内耗研究

对A位掺杂的La_1-xSr_xFeO_3-δ氧化物体系进行了低频内耗测量.研究发现此体系的内耗和模量-温度谱随Sr掺杂量（x）的不同而变化.当Sr含量x=0时,LaFeO_3-δ体系的内耗和模量在测量温度范围内（-150—380℃）没有明显变化;而当x=0.2,0.25,1/3以及0.5时,掺杂样品均观察到一个与正交—三角相变对应的相变型内耗峰P₁,且其峰温随x增加向低温移动.在x=0.25,1/3,0.5,0.6以及2/3的样品中还观察到一个弛豫型特征的内耗峰P₂,此峰伴随着模量的变化,可归于畴壁的运动.进一步分析表明畴壁是受氧空位钉轧的.在x=0.5,0.6以及2/3样品的模量-温度谱上呈现出的模量急剧变化是与三角—立方铁弹性相变有关的. 关键词： 内耗 畴壁 钉扎 铁弹性相变     

插层化合物LixTiS2中Li离子-空位二维有序结构稳定性的第一性原理研究

根据局域密度近似下的密度泛函理论，用第一性原理方法对TiS₂，LiTiS₂和Li_xTiS₂(x=1/4, 1/3, 1/2, 2/3, 3/4)有序系统进行了几何优化和总能量计算.将计算结果与已有的实验和理论结果进行了对比，得到的归一化结构参量增量Δa₀和Δc₀随离子浓度单调地增加，与实验结果符合较好.Li_{关键词： x}TiS₂')" href="#">Li_xTiS₂ 有序结构 第一性原理计算 密度泛函理论     

关于Zn1-xBexO电子结构和光学性质的研究

采用基于密度泛函理论和平面波赝势技术的CASTEP程序对Zn_1-xBe_xO合金电子结构和光学性质进行了计算.当0≤x≤1,其带隙从0.963 eV变化到7.293 eV.分析了晶格畸变和能带间排斥效应对带隙的影响.当Be含量x=0.125,0.25,0.375,0.5,0.625,0.75时,a/b轴压应变控制着带隙变化;当x=0.875,1时,c轴压应变控制着带隙变化.能带间的p-d排斥影响价带顶变动,Γ_1v与Γ_1c之间排斥影响导带底变动.这些能带间的排斥效应被用来分析Zn_1-xBe_xO带隙变动.另外,也分析了Zn_1-xBe_xO介电函数虚部ε₂. 关键词： 带结构 光学性质 应变 排斥     

六角相ErAx (A=H,He)体系弹性性质的第一性原理研究

本文采用第一性原理研究了六角相ErA_x (A=H, He)的弹性性质, 其中x=0, 0.0313, 0.125, 0.25, 分别讨论了体系中不同浓度的氢和氦对体系弹性性质的影响. 计算结果表明, 六角相铒-氢体系晶体的弹性常数、体弹模量、剪切模量、杨氏模量基本上随着晶体中氢的浓度增加而增加, 然而, 铒-氦体系的弹性常数、体弹模量、剪切模量和杨氏模量几乎随着氦浓度的增加而降低. 从电荷转移方面分析了氢和氦与Er的相互作用, 发现六角相ErH_x的弹性性质随H浓度的变化机理与ErHe_x随He浓度的变化机理不同. 关键词： 第一性原理 弹性性质 x')" href="#">六角相ErH_x x')" href="#">六角相ErHe_x     

Co含量对Fe3Si合金磁学性能的影响

采用基于密度泛函理论（DFT）的赝势平面波法,对过渡金属Co掺杂Fe₃Si进行几何结构优化,计算Co含量对Fe₃Si合金磁学性质的影响.研究表明：Fe_3-xCo_xSi的磁性主要来源于过渡金属元素Fe和Co,并且相对于A、C位的Fe和Co原子,B位Fe的原子磁矩较大;在0≤x≤0.75范围内,随着Co含量的增大,Fe_3-xCo_xSi的总磁矩缓慢减小,在0.75≤x≤1.5时,其总磁矩迅速地增大;A、C位Fe原子的磁矩和合金总磁矩的变化趋势相同,Co原子的磁矩随着Co含量的增大缓慢地增大,原子的磁矩变化与自旋向上和向下方向的电荷转移有关.     

B位等价掺杂SrBi4Ti4O15铁电材料的性能研究

采用了传统的固相烧结工艺,制备了不同Zr和Hf掺杂量的SrBi₄Ti_4-xZr_xO₁₅（x=000,003, 006,010,020）和SrBi₄Ti_4－xHf_xO₁₅（x=000,0005, 0015,0030,0060）的陶瓷 关键词： 4Ti_4-xZr_xO₁₅')" href="#">SrBi₄Ti_4-xZr_xO₁₅ 4Ti_4－xHf_xO₁₅')" href="#">SrBi₄Ti_4－xHf_xO₁₅ 铁电性能 介电性能     

TinLa（n=1—7）的密度泛函研究

采用密度泛函理论（B3LYP）和LANL2DZ基组,对Ti_n和Ti_nLa（n=1—7）的各种异构体进行优化,并计算了它们的振动频率和电子结构特征.通过分析掺杂La原子前后团簇的平均键长、对称性、束缚能、能级间隙和磁矩,讨论了La原子引起Ti_n（n=1—7）团簇各种性质的变化及其产生机理. 关键词： 密度泛函 基态结构 稳定性 磁矩     

Y掺杂SrTiO3晶体材料的电子结构计算

采用基于第一性原理的密度泛函理论平面波超软赝势法, 研究了Y掺杂SrTiO₃体系的空间结构和电子结构性质, 得到了优化后体系的结构参数, 掺杂形成能, 能带结构和电子态密度. 对比掺杂浓度为0125, 025, 033时,Sr_1-xY_xTiO₃和SrTi_1-xY_xO₃的掺杂形成能,发现Y替代Sr能形成更稳定的结构. 对Sr_1-xY_xTiO₃（x=0, 0125, 025, 033） 的结构进行了优化,结果表明Y替代Sr后, 随着掺杂浓度增大, 体系的晶格常数逐渐减小, 稳定性逐渐增强. 对不同掺杂浓度的Sr_1-xY_xTiO₃能带结构的计算结果表明：纯净的SrTiO₃是绝缘体, 价带顶在R点, 导带底在Γ点, 费米能级处于价带顶; 掺杂Y后, 费米能级进入到导带底中, 体系呈金属性;掺杂浓度越大,费米能级进入导带的位置越深,禁带宽度也近似变宽. 关键词： 3')" href="#">SrTiO₃ 电子结构 掺杂 VASP     

Stabilisation of Ce-Cu-Fe amorphous alloys by addition of Al

The present work describes the formation of amorphous alloys in the (Al_1?xCe_x)₆₂Cu₂₅Fe₁₃ quaternary system (0 ≤ x ≤ 1). When the amount of Ce falls in the range 0.67 ≤ x ≤ 0.83, the alloys obtained exhibit a completely amorphous structure confirmed by powder X-ray diffraction. Otherwise, at compositions x = 0.5, 0.58, 0.92 and 1, a primary crystalline phase forms together with an amorphous matrix. The crystallisation temperature (T_x) decreases with increasing Ce content, varying from 593 K for x = 0.5–383 K for x = 1. Composition x = 0.75 is considered as the best glass former, exhibiting a large supercooled liquid region of 40 K width that precedes crystallisation. In order to form bulk amorphous alloys, ribbons with this later composition were consolidated into few millimetre thick discs using pulsed electric current sintering at different temperatures, yet preserving the amorphous structure. Meanwhile, increasing temperature above 483 K triggers crystallisation of a primary phase isostructural to AlCe₃. Further increase in the temperature up to 573 K yields a higher fraction of the crystalline phase. Testing mechanical properties, using nanoindentation, revealed that both elastic modulus (E) and hardness (H) depend on the Al content, ranging from E = 85.6 ± 3.7 GPa and H = 6.2 ± 0.7 GPa for x = 0.5 down to E = 39.8 ± 1.0 GPa and H = 3.1 ± 0.2 GPa for x = 0.92.     

L12型铝合金的结构、弹性和电子性质的第一性原理研究

运用第一性原理方法研究了L1₂型铝合金相Al₃Sc和Al₃Zr的晶体结构、电子结构和弹性.结合能和形成能的计算表明,两种合金具有较强的合金化能力,且Al₃Zr较Al₃Sc具有更强的结构稳定性.电子结构分析表明,费米能级以下较多的价电子数决定了Al₃Zr具有较强的结构稳定性.计算并分析比较了两种合金相的单晶弹性常数（C₁₁,C₁₂和C₄₄）以及多晶弹性模量（体弹性模量B、剪切模量G、杨氏模量Y、泊松比ν和各向异性因子A）.通过对比实验和其他理论计算结果,进一步分析和解释了两种合金相的力学性质. 关键词： 铝合金 第一性原理 结构和电子性质 弹性     

利用Keating模型计算Si（1-x）Gex及非晶硅的拉曼频移

利用Keating模型计算了Si_（1-x）Ge_x合金中Si—Si,Ge—Ge和Si—Ge三种振动模态的拉曼频移,计算分别获得Ge浓度为01,05和09时,Si—Ge的振动拉曼频移分别为40275,41339和38815 cm^-1,这些结果与文献的实验结果符合,证明了Keating模型建立的关于原子振动模型是有效的,并可以利用拉伸压缩和相邻原子键之间弹性系数变化获得处于应变状态的拉曼光谱频率.利用Kea 关键词： Keating模型 拉曼光谱 （1-x）Ge_x')" href="#">Si_（1-x）Ge_x 非晶硅     

Theoretical prediction of structural,elastic and electronic properties of Si-doped TiCuGe intermetallics

The structural, elastic and electronic properties of TiCuGe_1?xSi_x alloys (x = 0, 0.25, 0.5, 0.75 and 1) were investigated by means of first-principles calculations within the framework of density functional theory (DFT). The calculated results demonstrate that the partial substitution of Si with Ge in TiCuGe leads to a decrease of lattice constants, and the optimized structural parameters are in agreement with the available experimental values. The results of electron density are compared with the theoretical and experimental data from the literature. From energetic point of view, it is found that with increase of Si content the structural stability of TiCuGe_1?xSi_x compounds increases apparently. The single-crystal elastic constants are obtained by computing stress–strain function according to Hooke's law, and then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of polycrystalline aggregates are derived. The calculated results show that among the TiCuGe_1?xSi_x alloys, TiCuGe_0.75Si_0.25 exhibited the largest stiffness, while TiCuGe_0.25Si_0.75 showed the best ductility. Finally, the electronic density of states (DOSs) are further studied and discussed.     

Supreme shear modulus predicted in the monocarbide system: the Rex W1–x C alloy

The energetic, mechanical and electronic properties as a function of composition for Re_x W_1–x C alloys in the WC structure have been investigated. It has been demonstrated that the shear modulus of WC can be enhanced by alloying with a small amount of Re, to a maximum shear modulus of 311 GPa at x = 0.23. The designed alloy is energetically stable and could be expected to be a potential extremely hard transition‐metal monocarbide, which is attributed to the strong metal–metalloid interaction with modulated valence electron concentration with respect to WC. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

First principles studies on the elastic,thermodynamic properties and electronic structure of Ti15−xMoxSn compounds

The structural, elastic, thermodynamic and electronic properties of the Ti_15−xMo_xSn compounds were systematically investigated by means of first-principles calculations based on the density functional theory (DFT). The calculated results demonstrate the Ti_15−xMo_xSn compounds still remain the stable β phase structure. The calculation of cohesive energy shows that the structural stability of the Ti_15−xMo_xSn compounds increases apparently with the increase of Mo content. According to Hooke's law, the single crystal elastic constants were obtained and show that all the calculated compounds keep mechanical stability. Then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of polycrystalline aggregates were calculated at zero pressure. The calculated results show that among these Ti_15−xMo_xSn compounds, Ti₄Mo₁₁Sn exhibits the largest stiffness while Ti₁₂Mo₃Sn shows the greatest ductility. The compounds Ti₁₂Mo₃Sn and Ti₁₁Mo₄Sn with the two lowest elastic Young's modulus of 61.01 GPa and 65.59 GPa are expected to be promising metallic biomaterials for implant applications. Besides, the Debye temperature Θ_D and the electronic density of states (DOS) are also investigated and discussed.     

Phase stability,elastic, electronic,thermal and optical properties of Ti3Al1−xSixC2 (0≤x≤1): First principle study

The structural parameters with stability upon Si incorporation and elastic, electronic, thermodynamic and optical properties of Ti₃Al_1−xSi_xC₂ (0≤x≤1) are investigated systematically by the plane wave pseudopotential method based on the density functional theory (DFT). The increase of some elastic parameters with increasing Si-content renders the alloys to possess higher compressive and tensile strength. The Vickers hardness value obtained with the help of Mulliken population analysis increases as x is increased from 0 to 1. The solid solutions considered are all metallic with valence and conduction bands, which have a mainly Ti 3d character, crossing the Fermi level. The temperature and pressure dependences of bulk modulus, normalized volume, specific heats, thermal expansion coefficient, and Debye temperature are all obtained through the quasi-harmonic Debye model with phononic effects for T=0−1000 K and P=0−50 GPa. The obtained results are compared with other results available. Further an analysis of optical functions for two polarization vectors reveals that the reflectivity is high in the visible–ultraviolet region up to ∼10.5 eV region showing promise as a good coating material.     

First-principles study of elastic and electronic properties of layered ternary nitride SrZrN2 under pressure

The structural, elastic, and electronic properties of SrZrN₂ under pressure up to 100?GPa have been carried out with first-principles calculations based on density functional theory. The calculated lattice parameters at 0?GPa and 0?K by using the GGA-PW91-ultrasoft method are in good agreement with the available experimental data and other previous theoretical calculations. The pressure dependence of the elastic constants and the elastic-dependent properties of SrZrN₂, such as bulk modulus B, shear modulus G, Young's modulus E, Debye temperature Θ, shear and longitudinal wave velocity V_S and V_L, are also successfully obtained. It is found that all elastic constants increase monotonically with pressure. When the pressure increases up to 140?GPa, the obtained elastic constants do not satisfy the mechanical stability criteria and a phase transition might has occurred. Moreover, the anisotropy of the directional-dependent Young's modulus and the linear compressibility under different pressures are analysed for the first time. Finally, the pressure dependence of the total and partial densities of states and the bonding property of SrZrN₂ are also investigated.