NVT系综下，用constraint methods 控制温度，步长取10fs,运行10000步左右后，看温度曲线在初始T波动不大，就是控制的还好，应该是达到平衡态的，可是看速度的麦克斯韦分布图，发现并不规则(如图），是什么原因？谢谢

这个麦克斯韦速度分布也还好了吧,建议看看能量上的变化或者构象这类的也较好

通常情况下，平衡态下出现速度分布不完全符合maxwell分布的原因是什么？谢谢

maxwell分布是不是要进行一段时间的统计才行？

要不然只在一个时刻进行统计的话，如果体系中粒子少，有限的速度值统计出来的速度分布可能就不好吧？

学习学习。。。

constraint methods  是啥方法？是不是乘个速度因子然后让他符合“能量均分定理”然后算T 保持恒温的方法？那本叫啥啥从算法到啥啥的 那本书里关于热浴的部分提到过 有关速度关联啥的有问题 不知道说的有关没？

1.6e-15S是不是10FS量级？（弱问一下）

First, velocity scaling schemes do not strictly follow the canonical ensemble, though in practice, the amount they deviate from canonical is quite small. (This can be measured by comparing the velocity distribution function with a Gaussian.) It is relatively easy to implement the second class of schemes, because they can be ``dropped'' in to existing codes using almost any integrator. However, they suffer the drawback that they are not time-reversible or deterministic, properties that become important in some advanced MD techniques. The third class are slightly more difficult to implement, but do not suffer from such drawbacks as time-irreversibility.

引用:

原帖由 redream 于 2008-9-9 16:31 发表
First, velocity scaling schemes do not strictly follow the canonical ensemble, though in practice, the amount they deviate from canonical is quite small. (This can be measured by comparing the velocit ...

hard to understand, but correspondingly to give the examples,thanks

引用:

原帖由 honghuzlj 于 2008-9-9 05:00 PM 发表

hard to understand, but correspondingly to give the examples,thanks

You should read the book named Understanding molecular simulation.

学习中，这个maxwell分布图是根据什么作的？Grid指的又是什么呢？

引用:

原帖由 redream 于 2008-9-9 22:51 发表


You should read the book named Understanding molecular simulation.

may i have your advice aiming at that what i asked for?

I think you should carefully review the process you are trying yo simulate and clarify the influence of  different thermosat such as  Aderson and Nose-Hoover on distibution, the latter one has problem of ergodic process, resulting unfavorable distibution obtained.

BTW,你的头像是谁啊，很合老夫胃口

Nose-Hoover会影响ergodic啊？能不能具体谈一谈吗？

楼主的图象是如何得到的?


弱弱的问一下.....菜鸟求助....