lammps解读命令系列.pdf

解读命令系列【1】【fix nve/limit command】 这个命令是设置初始状态常用命令，经典命令格式【fix 1 all nve/limit 0.1 】，我们一般直接用即 可【LJ 单位下】，注意此命令只能模拟开始使用，真正需要记录模拟信息时不能用。 命令语法 [b]Syntax:[/b] fix ID group-ID nve/limit xmax [list][*]ID, group-ID are documented in [color=#0000ff]fix[/color] command[*]nve = style name of this fix command[*]xmax = maximum distance an atom can move in one timestep (distance units)[/list] [b]Description:[/b] Perform constant NVE updates of position and velocity for atoms in the group each timestep. A limit is imposed on the maximum distance an atom can move in one timestep. [color=red]This is useful when starting a simulation with a configuration containing highly overlapped atoms.[/ color] Normally this would generate huge forces which would blow atoms out of the simulation box, causing LAMMPS to stop with an error. 【这段话 告诉我们这个命令是干什么的】 Using this fix can overcome that problem. Forces on atoms must still be computable (which typically means 2 atoms must have a separation distance 0.0). But large velocities generated by large forces are reset to a value that corresponds to a displacement of length [i]xmax[/ i] in a single timestep. 【通过你设定的距离计算速度，并用来标度】 [i]Xmax[/i] is specified in distance units; see the [color=#0000ff] units[/color] command for details. [color=red]The value of [i]xmax[/i] should be consistent with the neighbor skin distance and the frequency of neighbor list re-building, so that pairwise interactions are not missed on successive timesteps as atoms move.[/color] See the [color=#800080]neighbor[/color] and [color=#800080]neigh_modify[/ color] commands for details. 【如何设定最大限定的距离呢，这句话告诉我们，设置距离要和你的neighbor list 的设置有可比 性，不能比bin 大太多了，个人认为小没有关系，LJ 单位下我们设bin 一般是0.3 】 Note that if a velocity reset occurs the integrator will not conserve energy. On steps where no velocity resets occur, this integrator is exactly like the [color=#0000ff]fix nve[/color] command. Since forces are unaltered, pressures computed by thermodynamic output w