分子动力学模拟研究熔态硅的局部结构

采用Tersoff势，修正试用不同的粒子间相互作用距离R，S的取值，进行了液态硅的分子动力学模拟.模拟的结果表明，修正Tersoff势下得到的径向分布函数能与X射线衍射、中子散射实验相一致.模拟得到在液态硅中，Si的配位数为6.9，键长为0.254nm.分子动力学模拟表明，液态硅中Si原子间联接成一种网络状结构，但大多数Si原子与其近邻Si原子仍保持近似于正四面体的局部构型.键角概率分布出现两个峰值~57°和~102°.通过键序参量分析，得到在液态硅近邻结构中，正四面体构型约占82%，键取向波动方差为5. 关键词：

MOLECULAR DYNAMICS STUDY ON LOCAL STRUCTURE OF MOLTEN SILICON

A modified Tersoff potential developed by extending atomic interaction distancehas been applied to simulating the properties of liquid silicon with molecular dynamics. The radical distribution functions with coordination number 6.9 and bond length 0.254nm from the simulation are in good agreement with the experimental results from X-ray diffraction and neutron scattering. The configurations simulated indicate that a chain-network structure is formed among silicon atoms in liquid silicon,and a majority of atoms remain tetrahedral local structure with near-neighbour atoms. The presence of two peaks,~57° and ~102°,in bond angle probability distribution indicates a very complicated structure in liquid silicon. Based on the instantaneous configurations given by the simulation,the local structures in liquid states have been studied with bond-order parameter method. The results show there are ~82% tetrahedron structures in the near-neighbour structures in liquid state and the square deviation of bond-orientational luctuation is about 5.2°. The results also show that except thericosahedron structure,the non-tetrahedral structures may include some other near-neighbour structures.