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songp295

木虫 (小有名气)


[交流] 【求助】Gaussian中遇到这种问题如何解决?

请问:
Gaussian中遇到这种问题如何解决?(优化或单点)
Density matrix is not changing but DIIS error= 2.23D-06 CofLast=-8.30D-01.
The SCF is confused.
在l502死了。
谢谢大家!

[ Last edited by xuefei06 on 2008-12-8 at 23:22 ]
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wzslg

金虫 (著名写手)

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mingdong(金币+2,VIP+0):感谢您的帮助!
最简单的方法是加iop(5/13=1),如果还不行,可以试试以下的一些方法
1/
  - SCF=qc will probably solve the problem, albeit at a cost
  - Change the SCF converger to either SD, Quadratic or Fermi
2/
  - lower the symmetry of optimize with and optimize
    with the "nosymm" keyword
3/
  - scf=(Maxconventionalcycles=300,xqc)

I solved the problem using a variation on the first suggestion. Normally the scf took less than 80 cycles to converge. So i used scf=(Maxconventionalcycles=100,xqc) which resulted in a good compromise between using scf=qc and optimisation speed. In the case of the DIIS error the scf always took more than 100 cycles before the error, so by adding scf=(Maxconventionalcycles=100,xqc) the scf switched to qc after 100 cycles in the standard DIIS mode
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2楼2008-12-08 11:45:10
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