分子动力学模拟的主要技术

综述了分子动力学模拟技术的发展，介绍了分子动力学的基本原理，有关的有限差分技术，势函数的发展，初始条件和边界条件的选取，平衡态系综及其调控，感兴趣量的提取，分子动力学的特别用途以及与其他计算方法的结合，最后还指出了分子动力学模拟方法本身进一步研究的方向。

Deformation twinning and its effect on crack extension

Deformation twinning near a crack tip is observed in b.c.c. metal Mo based on molecular dynamics simulation at temperature T = 50 K and loading rate (K) over dot(II) = 0.0706 MPa m(1/2)/ps. The defor mation twinning is closely controlled by both the crystal geometry orientation and the stress distribution. The width of the deformation twin band is affected by the distance between the upper and lower crack surfaces. The twin plane and twin direction are (<1(1)over bar>2) and [(1) over bar 11], respectively. The initial crack extension occurs in the deformation twin region near the crack tip. The simulation shows that the extension direction of the crack is changed as the crack propagates over the twinning boundary.