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Bessel

木虫 (正式写手)

[求助] 请谁能解释一下Lammps里removing a "bias" from the atom velocities.

看了半天说明和其他文献,百思不得其解。
fix langevin command :

like other fixes that perform thermostatting, this fix can be used with compute commands that remove a "bias" from the atom velocities. E.g. removing the center-of-mass velocity from a group of atoms or removing the x-component of velocity from the calculation. This is not done by default, but only if the fix_modify command is used to assign a temperature compute to this fix that includes such a bias term. See the doc pages for individual compute commands to determine which ones include a bias. In this case, the thermostat works in the following manner: bias is removed from each atom, thermostatting is performed on the remaining thermal degrees of freedom, and the bias is added back in.

是不是说,比如我有一个沿X方向的couette flow,应为摩擦体系温度要升高,为了保持体系的温度,施加了langevin恒温器,但是在计算体系的温度时,要把x方向的动能刨除?不知道我理解的对不对?

关键问题是,“bias”到底是什么?我一直不理解。

谢谢!
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sdzjc1988

木虫 (小有名气)

【答案】应助回帖

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感谢参与,应助指数 +1
zh1987hs: 金币+1, 谢谢 2012-10-03 08:17:25
Bessel: 金币+10, ★★★★★最佳答案 2012-10-04 15:25:29
算温度用的是能量均分公式:3/2kbT=1/2mv2,减去bias就是把v里面的宏观速度减去,否则的话系统宏观运动的v也会用来算温度。
2楼2012-10-03 05:38:58
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Bessel

木虫 (正式写手)

引用回帖:
2楼: Originally posted by sdzjc1988 at 2012-10-02 22:38:58
算温度用的是能量均分公式:3/2kbT=1/2mv2,减去bias就是把v里面的宏观速度减去,否则的话系统宏观运动的v也会用来算温度。

宏观速度 is the streaming velocity,  Am I right?

sorry, I cannot input Chinese.
3楼2012-10-03 14:00:41
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sdzjc1988

木虫 (小有名气)

【答案】应助回帖

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zh1987hs: 金币+1, 谢谢 2012-10-03 22:49:18
引用回帖:
3楼: Originally posted by Bessel at 2012-10-03 14:00:41
宏观速度 is the streaming velocity,  Am I right?

sorry, I cannot input Chinese....

这要看你的steam veloctiy是不是系统的宏观速度了,这个应该比较好判断~
4楼2012-10-03 22:46:51
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