# VASP固定基矢优化结构方法

VASP优化的时候，用OPTCELL就限制真空层就行了。OPTCELL如下：

ISIF = 3 优化之后CONTCAR如下：

FCELL contains the forces on the basis vectors. These forces are used to modify the basis vectors according to the following equations:

FCELL 是个3 * 3的矩阵，包含了晶格矢量的受力，当ISIF = 3时，晶格矢量会按照如下的方法更新：

IF (ICELL(I,J)==0) FCELL(I,J)=0.0