液態鎵特殊結構之研究

Abstract

本計畫是本人過去所提的二年計畫 ”液態鎵熱力學及結構之研究” (NSC 97-2112-009-005-MY2) 的延續至第三年。在前面的計畫中，我們 對液態鎵的研討是根據於一原子間位能的模型。在本計畫中，除了此 一原子間位能模型的研究，我們將用第一原理計算探討液態鎵的特殊 結構；此係前一計畫未完成但值得繼續的研究。在所提計畫中，我們 研究的重點在於探討產生液態鎵特殊結構的物理原因。此特殊結構表 現在液態鎵靜態結構因子第一高峰右邊有一突出的部分，造成此特殊 結構的原因是液態金屬物理中數十年一直未解決的問題之一。本提計 畫包括三部分: (I) 簡介、 (II) 模型與模擬、 (III) 結構分析。在簡介 中，我將概述我們在前一計畫所完成的結果。在第二部分中，我將描 述我們過去研究所用的位能模型及用VASP 第一原理計算程式庫所做的 模擬，和用我們現有的電腦叢集執行計算時所會遭遇到的問題。在第 三部分中，結構分析包括四部份的計算: (A) 徑向分佈函數及靜態結構 因子，(B) 鍵結原子的徑向分佈函數及靜態結構因子，(C) 相鄰原子數 目分佈函數及角度分佈函數，(D) 局域方向有序參數

This project is actually an extension of my previous two-year project “ A study on thermodynamics and structure of liquid Ga” (NSC 97-2112-009-005-MY2) to the third year. In the previous project, our studies for liquid Ga are generally based on a model of pair potential. In this project, besides the model study, I extend our investigations by the first-principle simulation with the VASP package for the anomalous structure in liquid Ga, which is incomplete in the previous project but worth being continuous. In this proposal, our studies focus on the physical origin to produce the anomalous structure in liquid Ga, which exhibits a shoulder on the high-q side of the first peak of its static structure factor and is a long standing problem in liquid metal physics. The proposal contains three main sections: (I) Introduction, (II) Model and simulation and (III) Structural analysis. In the Introduction, I summarize what we have done in the previous project. In the section (II), I describe the model of interatomic pair potential that we have used and what we are going to perform by the VASP simulation package and what are the major difficulties that we will encounter as performing the simulation with our PC cluster. In the section of Structural analysis, we will do four kinds of analyses: (A) Radial distribution function and static structure factor, (B) Radial distribution function and static structure factor of bonded atoms, (C) Coordination-number distribution and bond-angle distribution, and (D) Local orientational order parameter.