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小木虫(金币+0.5):给个红包，谢谢回帖交流
ghcacj(金币+10, 模拟EPI+1): 精彩答疑，支持 2011-03-07 15:46:45
你大概没有理解 lattice和region 这两个命令的意思。 或者也可能没有很好地理解约化密度的概念，或者没有仔细阅读说明书。
我们看看说明书，Lattice的解释，有这么一段：
Lattices of style sq and sq2 are 2d lattices that define a square unit cell with edge length = 1.0. This means a1 = 1 0 0 and a2 = 0 1 0. A sq lattice has 1 basis atom at the lower-left corner of the square. A sq2 lattice has 2 basis atoms, one at the corner and one at the center of the square. 。。。。
上一段是说， Lattice sq这个命令，生成二维的方形晶格元胞，其元胞边长为1.0。对于sq 晶格，它的元胞里有一个原子，位于方形晶胞的左下角。
再往下看，有这一段，解释后边的scale这个数字：
For unit style lj, the scale argument is the Lennard-Jones reduced density, typically written as rho*. LAMMPS converts this value into the multiplicative factor via the formula "factor^dim = rho/rho*", where rho = N/V with V = the volume of the lattice unit cell and N = the number of basis atoms in the unit cell (described below), and dim = 2 or 3 for the dimensionality of the simulation. Effectively, this means that if LJ particles of size sigma = 1.0 are used in the simulation, the lattice of particles will be at the desired reduced density.
看清红字表示的公式。你现在是二维的晶格，dim=2，rho*=0.02是你输入的。rho=N/V, N是元胞中的basis原子数，上面说了，是一个，N=1，V是元胞体积，上面也说了，生成的是边长为1.0的方形元胞，所以有V=1.0，一算就知道 了，标定因子factor=sqrt(50)=7.07107。
region box block 0 20 0 20 -0.5 0.5
这个意思是生成20*20的格子，你现在一个元胞里有一个原子，20*20的晶格里面多少原子？400个。
至于后边关于相变的疑问，我还没有能够理解清楚你的问题。不大好回答。
[ Last edited by 老虎大王 on 2011-3-7 at 14:10 ] |
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