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buct2010金虫 (正式写手)
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[求助]
关于VASP手册中两个参数设置的问题，希望大家指点一下！
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（1）LMAXMIX （PAW赝势的设置参数） An additional flag controls up to which l quantum number the onsite PAW charge densities are passed through the charge density mixer and written to the CHGCAR file: LMAXMIX = l The default is LMAXMIX=2. Higher l-quantum numbers are usually not handled by the mixer, i.e. a straight mixing is applied for them (the PAW on-site charge density for higher l quantum numbers is reset precisely to the value corresponding to the present wavefunctions). Usually, it is not required to increase LMAXMIX, but the following two cases are exceptions: • L(S)DA+U calculations require in many cases an increase of LMAXMIX to 4 (or 6 for f-elements) in order to obtain fast convergence to the groundstate. • The CHGCAR file also contains only information up to LMAXMIX for the on-site PAW occupancy matrices. When the CHGCAR file is read and kept fixed in the course of the calculations (ICHARG=11), the results will be necessarily not identical to a selfconsistent run. The deviations can be (or actually are) large for L(S)DA+U calculations. For the calculation of band structures within the L(S)DA+U approach it is strictly required to increase LMAXMIX to 4 (d elements) and 6 (f elements). 问题： 是不是这个参数只对LSDA+U 计算有用？那如果用HF（Hartree-Fock）方法的时候也需要增大它吗（体系有d-f元素）？ （2）LRPA （光学计算中的随机相近似） LRPA = .TRUE. or .FALSE. Default: .FALSE. Usually local field effect are included on the Hartree level only (LRPA=.TRUE.). This means that cell periodic microscopic changes of the local potential related to the change of the Hartree potential are included. If LRPA= .FALSE., however, changes of the Hartree potential and the exchange correlation potential are included. This usually increases the dielectric constants. The final values for the dielectric matrix can be found in the OUTCAR file after the lines. MACROSCOPIC STATIC DIELECTRIC TENSOR (including local field effects in RPA (Hartree)) For LRPA=.FALSE. the dielectric matrix is written after the lines: MACROSCOPIC STATIC DIELECTRIC TENSOR (including local field effects in DFT) The dielectric constants without local field effects is always determined (irregardless of LRPA). The piezoelectric tensors and the Born effective charges as well as the ionic contributions the to dielectric tensor are only calculated for LRPA=.FALSE. 问题： 这个随机相近似对于介电函数有什么影响？是不是可以理解为DFT计算的时候设置LRPA = .TRUE.；HF（Hartree-Fock）计算的时候设置LRPA = .TRUE.？ [ Last edited by buct2010 on 2012-2-29 at 09:23 ] |
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【答案】应助回帖
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fzx2008(金币+1): 谢谢分享 2012-02-29 11:41:17
buct2010(金币+5): ★有帮助 谢谢版主，你给的链接是翻译了手册上LRPA，你可能没看清我在每个参数下提的问题。我是想针对这两个参数的设置提一些问题~ 2012-02-29 15:11:09
fzx2008(金币+1): 谢谢分享 2012-02-29 11:41:17
buct2010(金币+5): ★有帮助 谢谢版主，你给的链接是翻译了手册上LRPA，你可能没看清我在每个参数下提的问题。我是想针对这两个参数的设置提一些问题~ 2012-02-29 15:11:09
2楼2012-02-29 11:27:20
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3楼2012-03-08 08:14:04
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