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yq2240711

金虫 (正式写手)

[交流] 【求助】如何从算出的E-a数值拟和出晶格常数a0

如何从算出的一系列E-a数值拟和出晶格常数a0
如何利用物态方程拟和晶格常数?

[ Last edited by yq2240711 on 2009-11-21 at 21:19 ]
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zdd2008

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yjmaxpayne(金币+4,VIP+0):谢谢分享 11-12 19:12
引用回帖:
Originally posted by xirainbow at 2009-11-11 22:35:


请问,如何使用物态方程拟合正交,单斜,三斜晶系的情况呢:)?

[ Last edited by xirainbow on 2009-11-11 at 22:38 ]

物态方程拟合的是体积与能量,体积与压力之间的关系!因此对于正交,单斜,三斜晶系也适用!!呵呵!!
我明白你的意思,比如拿正交来讲,拟合得到平衡体积后,根本不知道a,b,c分别是多少!此时可以采用全弛豫的a:b:c来确定!这是我的处理方法!呵呵!!不知道讲明白了没有!!
8楼2009-11-11 23:49:43
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xirainbow

木虫 (正式写手)

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yq2240711(金币+3,VIP+0): 11-11 19:35
yjmaxpayne(金币+1,VIP+0):谢谢解答 11-11 20:01
用pwscf可以直接拟合,参看:
http://blog.sina.com.cn/s/blog_5f15ead20100f5jx.html

可以直接用泰勒展开去拟合么?
请高人帮忙;)
2楼2009-11-11 19:34:39
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zdhlover

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yq2240711(金币+1,VIP+0): 11-11 20:40
yjmaxpayne(金币+5,VIP+0):非常感谢提供信息 11-11 21:17
On the other hand, we may use a relatively simple approach to refine the determined equilibrium
value of the lattice constant by fitting our sampled data points to a second order
polynomial of the form

P(a)=A(a-a0)*(a-a0)+B(a-a0)+c
We may then choose the minimum of P(a)
amin=a0-B/(2A)
as the value of the lattice constant . We now set a0=2.999 (the central point of the interval) and let h= 0.01 Rydberg (the equidistant spacing between sample points). In addition, using a few algebraic manipulations leads to the following analytic expressions for the two constants A and B
:

A=(E(a0+h)+E(a0-h)-2E(a0))/(2h*2h)
and
B=(E(a0+h)-E(a0-h)))/2h

then you can get the lattice constant :amin=a0-B/(2A)
3楼2009-11-11 20:06:57
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xirainbow

木虫 (正式写手)

引用回帖:
Originally posted by zdhlover at 2009-11-11 20:06:
On the other hand, we may use a relatively simple approach to refine the determined equilibrium
value of the lattice constant by fitting our sampled data points to a second order
polynomial of th ...

您提供的信息太好了:)
请问,您从哪里获得的这些说明 ?
能给个链接么?
谢谢啦;)
4楼2009-11-11 20:54:09
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