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goalry

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[交流] 什么是均方位移?

均方位移是描述的什么概念,它的意义在于什么?
均方位移为什么能和扩散联系?

下面的附件是一个均方位移的公式,其中的M、N分别代表意思?

现在还不知道均方位移的物理含义呢,他为什么就能和扩散系数联系起来?

[ Last edited by goalry on 2007-12-22 at 16:28 ]
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tobyjerry

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The mean square displacement (msd) is a measure of the average distance a molecule travels.  It is defined



In this equation, ri(t)-ri(0) is the (vector) distance traveled by molecule i over some time interval of length t, and the squared magnitude of this vector is averaged (as indicated by the angle brackets) over many such time intervals. Often this quantity is averaged also over all molecules in the system, summing i from 1 to N and dividing by N.

The MSD contains information on the atomic diffusivity.

N是分子数,M是指测的次数

[ Last edited by tobyjerry on 2007-12-21 at 16:11 ]
2楼2007-12-21 13:10:27
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