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tailor

金虫 (小有名气)

[交流] 【求助】siesta计算中,如何进行BSSE修正?

即基组重叠误差,全称为Basis Set Superposition Error(BSSE)。对于双分子A和B的相互作用能应该表述为E_interaction = E_AB - E_A - E_B + E_BSSE。第三项即为修正项。对于弱相互作用,E_BSSE所占E_interaction的比例往往不小,甚至超过它,如果不进行校正,可能正负号都不对。
      这些也是从网上查到的,但是网上主要介绍的都是高斯算法中的BSSE修正,由于本人用siesta算,想麻烦各位高手多多赐教!!
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tailor

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请教老外,得到的回复


zxzj05(金币+1):谢谢回帖交流 2010-09-25 22:34:07
引用回帖:
Originally posted by zhangguangping at 2010-09-06 21:30:41:

为什么要算这个?什么体系才学要考虑BSSE修正啊?
我不是很懂,但是对你的问题很感兴趣,想问问你。

What we calculated is the Basis Set Superposition Error (BSSE) that is an error occurring when you use a finite basis set to study, for example, a chemical reaction. In a tipical reaction you calculate the electronic structure of the reactants separately, let us say A and B, and then the electronic structure of the product, A+B. What happens in this case is that you are using different basis sets to represent the reactants in each step of the calculation. When you calculate the isolated reactant A, you use the basis set of A, and the electrons of A will be arranged spatially on these provided orbitals. However, when you put both systems together in the A+B, the electrons of A will have now a greater spatial freedom, since they can now occupy orbitals coming from B. The same happens with B. You have different basis sets to distribute the electrons of A in the two situations.
To correct this, you need to recalculate the energy of the isolated reactants (A and B) by considering the basis set of both reactants, i.e., the calculations of the isolated reactant A will now include the basis sets of B (without the system B itself). It needs to be done for each configuration that you take into account in the reaction of A+B. Now you will have the same basis set for the isolated reactants and the product.
You can look for more information searching for "counterpoise correction"
5楼2010-09-10 19:36:33
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ifmc1234

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★ ★ ★
tailor(金币+2):谢谢参与
qasd(金币+2):谢谢 2010-09-11 18:57:22
引用回帖:
Originally posted by tailor at 2010-09-06 21:06:56:
即基组重叠误差,全称为Basis Set Superposition Error(BSSE)。对于双分子A和B的相互作用能应该表述为E_interaction = E_AB - E_A - E_B + E_BSSE。第三项即为修正项。对于弱相互作用,E_BSSE所占E_interaction的 ...

不知道你算的是分子还是固体,建议不要用它来讨论。你可在userguide里搜一下,我没看有什么人用siesta讨论过BSSE,在userguide里的27页提到了BSSE。不过具体怎么做还不知道。说明书中只提到PAO.Basis里设置时,用Ghost原子可以处理BSSE。不过如果根据你上面的定义,我想可以这样E_interaction = E_AB - E_A - E_B + Sum_E_BSSE,其中Sum_E_BSSE为A,B单个的BSSE之和。也就是说用鬼原子来处理BSSE,然后根据上面求的
2楼2010-09-06 21:29:23
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zhangguangping

木虫 (著名写手)


tailor(金币+2):谢谢参与
引用回帖:
Originally posted by tailor at 2010-09-06 14:06:56:
即基组重叠误差,全称为Basis Set Superposition Error(BSSE)。对于双分子A和B的相互作用能应该表述为E_interaction = E_AB - E_A - E_B + E_BSSE。第三项即为修正项。对于弱相互作用,E_BSSE所占E_interaction的 ...

为什么要算这个?什么体系才学要考虑BSSE修正啊?
我不是很懂,但是对你的问题很感兴趣,想问问你。
弘德明志博学笃行
3楼2010-09-06 21:30:41
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zhangguangping

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zxzj05(金币+1):谢谢回帖交流 2010-09-25 22:34:19
引用回帖:
Originally posted by tailor at 2010-09-10 12:36:33:



What we calculated is the Basis Set Superposition Error (BSSE) that is an error occurring when you use a finite basis set to study, for example, a chemical reaction. In a tipical reaction you ...

意思就是说因为计算一个体系的时候前后,使用的基组不一样大造成了一定的误差,这个误差需要修正。如果第二次引入的那部分基函数和第一次的基函数都正交的话,也就是各自是一个子空间的话,这个修正就不用做了吧?
弘德明志博学笃行
6楼2010-09-11 10:02:01
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