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snowmami

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[交流] 【求助】wien2k-FAQ实在是看不懂，哪位高手帮我翻译下？

下面的文字对我很重要，但实在看不懂，很着急，难者不会，会者不难，各位高手能否帮忙翻译下？
WIEN2k-FAQ: Setup of antiferromagnetic calculations?

©2001 by P. Blaha, K. Schwarz and J. Luitz

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FAQ Index

Setup of antiferromagnetic calculations requires some tricks which will be described below:

1. You need to construct a unit cell which allows for the desired AF ordering. E.g. for bcc Cr you have to put "P" lattice and 2 NON-equivalent atoms at (0,0,0) and (0.5,0.5,0.5). In order to make nn working properly, you should also specify different labels in the "name(3:10)"-field for the two AF-atoms (Eg. "Cr1" and "Cr2"

.
2. Run init_lapw. nn and/or sgroup determines equivalent atoms. Accept eventually the new struct_nn file (You may have to use the same procedure as described in faq:supercells).
3. Edit case.inst and flip the spin of the second AF atom. This means you must invert the spin-up and dn occupation of this atom. Atoms which carry no spin (e.g. an O between two AF metal atoms) should be made non-spinpolarized by setting equal numbers of up and dn-electrons.
   For AFM NiO case.inst looks like:

   Ni
   Ar 3 5
   3, 2,2.0  N
   3, 2,2.0  N
   3,-3,3.0  N
   3,-3,1.0  N
   4,-1,1.0  N
   4,-1,1.0  N
   Ni
   Ar 3 5
   3, 2,2.0  N
   3, 2,2.0  N
   3,-3,1.0  N <=== spin flipped
   3,-3,3.0  N <=== spin flipped
   4,-1,1.0  N
   4,-1,1.0  N
   O
   He 3 5
   2,-1,1.0  N
   2,-1,1.0  N
   2, 1,1.0  N
   2, 1,1.0  N
   2,-2,1.0  N  <=== equal occup for up/dn
   2,-2,1.0  N  <=== equal occup for up/dn
   ****    End of Input
   ****    End of Input

   This case.inst file can also be prepared by the new: instgen_lapw -ask , where you can specify for each atom spin-up, dn or non-magnetic configurations.
4. Continue with init_lapw (rerunning lstart) and select "spin-polarized" calculations.
5. You may now run an scf cycle using runsp_lapw; or
6. You may try to select "AFM-calculations", generate "case.inclmcopy" and use "runafm_lapw". For simplest use of "afminput" you should provide the nonmagnetic (or ferromagnetic) supergroup in "case.struct_supergroup". Please read the usersguide for more details. (help_lapw and search for AFM).

   If you succeed to generate proper input files, you can do the scf-cycle by "runafm_lapw", which will save at least half the computer time, since only one spin-direction is calculated and the other one is generated by symmetry. However, since these programs are little tested, I recommend to check the final results of "runafm_lapw" by
7. "runsp_lapw". If the charge distance (grep

IS case.scf) remains small and the magnetic moments do not change, runafm_lapw was successful, otherwise continue with runsp_lapw until convergence.

Peter Blaha,

[ Last edited by snowmami on 2010-12-8 at 21:59 ]

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1楼 2010-12-08 21:58:40

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gzqdyouxia

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sunyang1988(金币+3):辛苦了 2010-12-11 19:23:30

进行反铁磁计算的步骤：
1、创建一个AF需要的单胞。例如：对于体心Cr，应该选取晶格对称性P（取消对称性），2个不等价原子位置(0,0,0)和(0.5,0.5,0.5).为了使nn选取合适，应该给两个AF原子不同的标记（例如：Cr1＆Cr2）
2、运行init_lapw。nn或者sgroup需要等价原子，接受新结构文件struct_nn
3、编辑case.inst并且翻转第二个AF原子自旋。这意味着翻转这个原子占据态的上下自旋。对于不带自旋的原子（例如O原子），应该使用非自旋极化（上下自旋电子数相等）。
对于AFM的NIO 的case,inst为：略
＊＊＊这个case.inst文件也可以用instgen_lapw -ask命令产生，这个命令可以标记任何原子为上自旋，下自旋，或者非磁。（我在计算AFM时都是使用这个命令）
4、继续init_lapw并且选择自旋极化计算，完成初始化。
5、初始化完成后运行runsp_lapw或者进行第6操作
6、选择AFM-calculations，生成case.inclmcopy文件，使用runafm_lapw。对于afminput最简单的使用，你应该用case.struct_supergroup提供非磁或铁磁supergroup。详细阅读userguide（help_lapw and search for AFM）
成功生成输入文件后，可以运行自恰循环通过runafm_lapw。因为只计算上自旋，其他自旋方向的计算都是通过对称性完成的，所以可以减少一般的计算时间。
7、如果charge distance 仍然很小，磁矩没有改变，运行runsp_lapw，再runafm_lapw。如果还不成功继续runsp_lapw直到收敛。

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2楼2010-12-11 19:15:56

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