比較兩種位能函數在矽沉積模擬系統之異同

Abstract

位能函數決定原子的運動，也決定系統的特性。本論文利用分子動力學（Molecular dynamics）模擬以分子束法（Beam epitaxy）進行的矽沉積系統。矽原子間的位能關係分別採用S.W.及B.H.兩種位能函數，並藉由比較兩種位能函數和模擬所得的晶體結構的差異，從而得知兩位能函數的優劣。 常見於分子動力學模擬中的空間分割（Cell subdivision）技術，目前僅適用於two-body potential的位能計算。本論文以原有的空間分割理論為基礎，提出一套適用於three-body potential計算的空間分割方式。希望藉由本方法有系統的空間選取，減少重覆計算和除去作用力有效範圍外的計算，進而大幅降低模擬程式的計算量。本論文詳細說明此一新式的空間選取法則，並將其應用於本論文的程式模擬上。

Potential functions, which describe the energy relations between atoms in a material, can determine the movements of atoms and thus properties of a material. In the thesis, we use the molecular dynamics (MD) to simulate a beam expitaxy silicon deposition system. Two well-known potential functions for silicon atoms, S.W. and B.H., were used in these simulations respectively for comparisons. “Cell subdivision” techniques are very popular in MD simulations because they can greatly reduce the computation load. However, they are applicable to the calculations of “two-body potential,” but not the “three-body potential.” In this thesis, we develop a systematic way of selecting spaces in cell subdivisions so that the method can be extended to the case of “three-body potential.” This method is discussed in details and used in the MD simulations in this thesis.