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[交流] 【讨论】U值是怎么确定的？

用vasp计算时需要加U，但是这个U值是怎么确定的呢，跟据参考文献还是通过计算得到，怎么样计算，请各位高人指点，非常感谢！！！

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1楼2009-06-23 14:00:18

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天空空

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qasd(金币+3,VIP+0):xiexie~ 6-27 13:21

U值是可以由第一性原理确定的计算出来的：
请参考以下两篇文章：

N. J. Mosey and E. A. Carter, Physical Review B, 76, 155123 (2007)
N. J. Mosey, P. Liao, and E. A. Carter, Journal of Chemical Physics, 129, 014103 (2008)

参见：

http://www.princeton.edu/mae/peo ... /research/software/

GAMESS - AIDFT+U (ab initio DFT+U)
Goal:
Evaluate ab initio the Coulomb and exchange parameters for DFT+U calculations. DFT+U theory is based on DFT, but the intra-atomic Coulomb and exchange interactions of localized valence electrons are effectively treated at the Hartree-Fock level of theory. DFT+U theory can correct the self-interaction errors in DFT, given the average Coulomb (U) and exchange (J) interactions of these localized valence electrons as input. To obtain these two parameters, previously researchers either empirically fitted them or performed constrained DFT calculations. We recently proposed instead to evaluate the U and J using unrestricted Hartree-Fock calculations on electrostatically embedded clusters.

Implementation in GAMESS:
The method used to evaluate these parameters is based on unrestricted Hartree-Fock calculations. A few subroutines were modified to get GAMESS to calculate U and J.
The modifications to each subroutine are:
gamess.src: check input files and variables;
prppop.src: get Mulliken populations for calculating U and J;
int2a.src: calculate the onsite two-electron integrals in the basis of the atomic orbitals;
rhfuhf.src: extensive modifications to calculate U and J;
scflib.src: calculate the Coulomb and exchange integrals through building the Fock matrix with direct SCF methods.

[ Last edited by 天空空 on 2009-6-27 at 12:55 ]