Electron Theory and Statistical Thermodynamics for Tegragonal Distortion

四方畸变的电子理论和统计热力学

• 批准号: 04452266
• 负责人: MOHRI Tetsuo
• 金额: $ 3.01万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452266/
• 关键词: Tetragonality; Electron theory; Lattice displacement; Structural transition CVM; Pseudo potential; Programd cell death; Interatomic potential; 第一原理計算; カー・パリネロ法; Siの弾性定数; 有効相互作用エネルギー

The first-principles calculations of a phase diagram and thermodynamic quantities have been so far limited to the system with a high symmetric crystal structure. In reality, however, one finds various alloysystems with the tetragonal distortion. The deviation from the full cubic to tetragonal symmetries is not only closely related to the phase stability of ta given system but also affects various mechannical properties. The main objective o fht eproposed project is to establish the computational and theoretical basis to study tetragonal distortion effects based on electronic theory and statistical theomadynamics. Followings are the main outcomes of the projects.1. In order to derive the distant pair interaction energies which play crucial role in stabilizing the tetragonal structure, we employed the Cluster Expansion Method and extracted pair interactions up to fourth nearest neighbor.2. By employing the first-principles pseudopotential theory, we calcualted the lattice constant, Poisson's ratio and other elastic properties as a function of tetragonal distortion and optimized the structure.3. The tetrahedron approximatin of the Cluster Variation method of statistical mechanics is modified so that the tetragonal to calcualte the free energy as a fnctin of tetragonal distortion. The program is applied to culculate a disorder-L1o phase diagram with the tetragonal distortino explicitely incorporated in the L1o ordered phase.

到目前为止，相图和热力学量的第一性原理计算仅限于具有高度对称晶体结构的系统。然而，在现实中，人们发现各种合金体系具有四方畸变。从全立方对称到四方对称的偏差不仅与体系的相稳定性密切相关，而且还影响着体系的各种力学性能。本课题的主要目的是建立基于电子学理论和统计动力学的研究四方畸变效应的计算和理论基础。以下是项目的主要成果。为了得到在稳定四边形结构中起关键作用的远端对相互作用能，我们采用了聚类展开法，提取了直到第四近邻的对相互作用。利用第一性原理赝势理论，计算了晶格常数、泊松比和其他弹性性能作为四方畸变的函数，并对结构进行了优化。对统计力学的聚类变分法的四面体近似进行了修正，使四面体作为四面体畸变的函数来计算自由能。应用该程序计算了l10有序相中显式包含四方畸变的无序- l10相图。

项目成果

S.Takizawa,E.Wakatsuki,T.Mohri: "Study on the tetragonal distortion effects on the phase stability of Si" (投稿予定).

S.Takizawa、E.Wakatsuki、T.Mohri：“四方畸变对Si相稳定性影响的研究”（待提交）。

Tetsuo Mohri,Satoshi Takizawa,Masanori Suzuki: "THEORETICAL STUDY ON PHASE STABILITY FOR CUPt Ll_1 PHASE" Proc.The Third Japan International SAMPE Symp.“Advanced Materials". 2. 1264-1269 (1993)

Tetsuo Mohri、Satoshi Takizawa、Masanori Suzuki：“CUPt Ll_1 相的相稳定性理论研究”Proc.第三届日本国际 SAMPE Symp。“先进材料”2. 1264-1269 (1993)。

Tetsuo MOHRI, Satoshi TAKIZAWA and Masanori SUZUKI: "THEORETIDCAL STUDY ON PHASE STABILITY FOR CuPt L11 PHASE" Proc. The Third Japan International SAMPE Symp. "Advanced Materials" ed. by T.Kishi et. al.Vol. 2. 1264-1269 (1993)

Tetsuo MOHRI、Satoshi TAKIZAWA 和 Masanori SUZUKI：“CuPt L11 相的相稳定性理论研究”Proc。

S.TAKIZAWA, E.WAKATSUKI and T.MOHRI: "Study on the tetragonal distortion effects on the phase stability of Si." in preparation.

S.TAKIZAWA、E.WAKATSUKI 和 T.MOHRI：“四方畸变对 Si 相稳定性影响的研究”。

Tetsuo Mohri,Satoshi Takizawa,Masanori Suzuki: "THEORETICAL STUDY ON PHASE STABILITY FOR CuPt L1,PHASE" Proc.The Third Japan International SAMPE Symp. “Advanced Materials". 2. 1264-1269 (1993)

Tetsuo Mohri、Satoshi Takizawa、Masanori Suzuki：“CuPt L1 相稳定性的理论研究”Proc.第三届日本国际 SAMPE Symp。2. 1264-1269 (1993)。