材料期刊网

Vibration Effects on the Structural Stability of Al-Ti Intermetallics by First-principles Calculations

Hui Zhang Shaoqing Wang

材料科学技术（英文）

The structural stability of the intermetallics AlTi₃, Al₂Ti, Al₃Ti₄ and Al₃Ti in the Al-Ti system has been investigated using density functional theory (DFT) and density functional perturbation theory (DFPT). The calculated ground-state convex hull is in agreement with the experimental researches. Al₃Ti₄ (hP7) is metastable at 0 K and may be stabilized as the temperature increases due to the effects of the vibration entropy. For Al₂Ti, r-Al₂Ti is stable at 0 K and h-Al₂Ti is stabilized by the vibration entropy at high temperatures. Al₃Ti (tI16) is unstable considering vibration effects and Al₃Ti (tI8) is the most stable structure at 0 K.

关键词: First-principles , Al-Ti , 振动 , 晶体结构

First-principles Calculation Assisted Thermodynamic Modeling of Ti-Co-Cu Ternary System

Y.J. Yang X.M. Tao W.J. Zhu Z.H. Long H.S. Liu Z.P. Jin

材料科学技术（英文）

Thermodynamic assessment of Ti-Co-Cu ternary system has been carried out by combining first-principle calculation and CALPHAD method. Firstly, formation enthalpies of stable and hypothesized compounds were calculated by first-principles method. Then, based on reported experimental information, a thermodynamic description of the Ti-Co-Cu ternary system was performed. Solution phases were treated as substitutional solutions of which excess Gibbs energies were formulated by Redlich-Kister polynomial, and the intermediate phases were described with sublattice models. All measured isothermal sections were reasonably reproduced. In addition, liquidus projection of this ternary system was further calculated, which may be useful for relevant materials processing.

关键词: First-principle , assessment , phase diagram , First-principles

First-Principles Study of the Polar TiC/Ti Interface

Limin LIU , Shaoqing WANG , Hengqiang YE

材料科学技术（英文）

The interface structure, work of adhesion, and bonding character of the polar TiC/Ti interface have been examined by the first-principles density functional plane-wave pseudopotential calculations. Both Ti- and C-terminated interfaces including six different interface structures were calculated, which present quite different features. For the Ti-terminated interface, the interfacial Ti-Ti bond has a strong metallic and weak covalent character; while for the C-terminated interface, the interfacial bond is a strong polar covalent interaction between the Ti-3d and C-2p orbital. The work of adhesion of C-terminated interface is nearly 9 J/m2 stronger than that of the Ti-terminated. It is found that each termination has relatively large work of adhesion, which is consistent with other polar interfaces.

关键词: First-principles , null , null , null

First-principles Study of NiAl Alloyed with Rare Earth Element Ce

You Wang

材料科学技术（英文）

The structural, elastic, and electronic properties of NiAl alloyed with rare earth element (REE) Ce have been investigated by using density functional theory (DFT). It is found that Ce has a strong Al site preference and causes lattice distortion of NiAl. The calculation of elastic constants shows that Ce increased both the hardness and the ductility of NiAl, which could be explained by the formation of new ionic bonds between Al (and Ni) and Ce and the enhancement of covalent bonds in Ni₈Al₇Ce. Our results are in good agreement with the available experimental data and other theoretical results.

关键词: Point defects

First-principles Study of NiAl Alloyed with Rare Earth Element Ce

You Wang

材料科学技术（英文）

The structural, elastic, and electronic properties of NiAl alloyed with rare earth element (REE) Ce have been investigated by using density functional theory (DFT). It is found that Ce has a strong Al site preference and causes lattice distortion of NiAl. The calculation of elastic constants shows that Ce increased both the hardness and the ductility of NiAl, which could be explained by the formation of new ionic bonds between Al (and Ni) and Ce and the enhancement of covalent bonds in Ni₈Al₇Ce. Our results are in good agreement with the available experimental data and other theoretical results.

关键词: Point defects

金属Zr热力学性质的第一原理研究

聂耀庄 , 谢佑卿 , 李小波 , 彭红建

金属学报

应用基于密度泛函与密度泛函微扰理论的平面波赝势方法计算了一组不同晶格常数下hcp结构金属Zr的声子谱及相应的静态总能，由此得到不同晶格常数下的自由能，由准谐近似及自由能极小判据得到自由能与温度的关系，进而计算了热膨胀系数、体弹性模量、定容及定压摩尔热容与温度的关系，计算结果在较宽的温度范围内与实验相符。对热膨胀系数，同时应用德拜-格林奈森模型进行了计算，并与第一原理方法的结果进行了比较。对摩尔热容的计算考虑了电子的贡献，表明在高温区电子热容的贡献不能忽略

关键词: 第一原理计算 , calculations , Thermal properties , Phonons

β-Ga2O3掺Al的电子结构与能带特性研究

郑树文 , 范广涵 , 皮辉

功能材料 doi:10.3969/j.issn.1001-9731.2014.12.020

采用第一性原理的平面波超软赝势方法,对β-Ga2O3掺Al的AlxGa2-xO3(x=0,0.5,1,1.5,2)合金进行结构优化、电子态密度和能带特性的研究。结果显示,Alx Ga2-x O3为间接宽能隙材料,能隙是由导带底Ga 4s态和价带顶 O 2p 态共同决定,其弯曲系数分别为0.452 eV(直接)和0.373 eV(间接)。当增大Al的掺杂量,Alx Ga2-x O3的体积变小,总能量升高,能隙逐渐增大,这与实验结果相一致。

关键词: 第一性原理 , β-Ga2O3 , Al掺杂 , 电子结构 , 能带特性

First-Principles Study of the Polar TiC/Ti Interface

材料科学技术（英文）

关键词:

第一原理研究氧空位对BaTiO3晶体的电子结构和光学性质的影响

应杏娟 , 倪争技

人工晶体学报

根据密度泛函理论,采用模拟计算软件CASTEP计算了含有氧空位钛酸钡晶体的电子结构和光学性质.结果表明,氧空位的存在没有在禁带中引入缺陷能级,但氧空位的存在对晶体的光学性质产生显著的影响.并得到氧空位的存在将引起钛酸钡晶体出现440～450 nm吸收峰的结论.

关键词: 第一性原理 , 电子结构 , 钛酸钡 , 光学性质 , 氧空位

Eu和N共掺TiO2的结构及光催化性能研究

陈浩 , 姚兰芳 , 吴佳文 , 杨思雨

低温物理学报

本文基于第一性原理的平面波超软赝势计算TiO2和Eu-N-TiO2的几何结构、重叠布局数、Mulliken电荷、能带结构、态密度、电荷分布和光吸收.研究发现Eu和N共掺后有额外电子进入价带,使费米面上移且态密度变平缓,有利于载流子的产生和运输.共掺后产生了离子性更强的化学键,能吸收波长较长的光,并且禁带宽度降低,发生红移,提高了TiO2的光催化活性.同时采用了溶胶-凝胶法制备TiO2和Eu-N-TiO2复合纳米材料,对其进行XRD、UV-vis和SEM表征,并通过光降解甲基橙评估其光催化活性.研究发现Eu和N共掺能抑制TiO2从锐钛矿相向金红石相转变和晶粒长大,有利于提高TiO2的光催化活性.此外,Eu-N-TiO2在250nm后的紫外光和可见光下的光催化活性都比TiO2高,经过2个小时照射,在紫外光和可见光下对甲基橙的光降解率分别达到98.54％和69.59％.

关键词: Eu-N-TiO2 , 第一性原理 , 溶胶凝胶法 , 光催化活性