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otuvlh

金虫 (小有名气)

[求助] 表面能的计算

LZ刚学MS,计算Al(111)面表面能时出现了以下几个问题,求高人解答:
1.surface thickness,我看文献中取的都是3,5,7,9。想问一下为什么不取偶数呢?
2.采用LDA的算法,也优化了晶体结构,根据公式: 表面能=(Eslab- n x Ebulk)/2A算的,Ebulk取的是0.5*(Eslab(n+2)-Eslab(n))的平均值。没constraint atom,感觉应该没什么问题,得出的结果大概都在0.82J/m2,而实验值和文献中的值都在1J/m2左右。所以不太清楚是哪里出了问题,求高手提供点思路
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jpchou

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★ ★ ★ ★ ★
fzx2008: 金币+5, 谢谢指导,辛苦 2013-12-13 20:25:32
???????:
9?: Originally posted by otuvlh at 2013-12-13 08:57:05
??л?????????????????????????
1.?漰??????Al(111)??????????adhesion or adhesive transfer????Al??111????????????????????м?????????1J/m2????????????????????????????????? ...

1.?漰??????Al(111)??????????adhesion or adhesive transfer????Al??111????????????????????м?????????1J/m2???????????????????????????????????????????0.2J/M2??????20???????????????????????????????????????????????????????????????????п???????reproducible??,????????????????????????????????????e-cutoff??K-Points?????????ó??????????0.82J/m2??????????LDA??Al???????????????????????

????N????????
??????? DFT ??????S??????
??????? LDA ??????? Al ???????????????????
?@?????????????????y???????Q??
???????? ENCUT=3000 , kpoint=100x100x1
???}???h????~
????@????????浽 LDA ?@?? approximation ??????
????????@ 20% ???`??
??o????PAPER?? 1993 ??????~??S???c????
?????? http://www.jmst.org/fileup/PDF/pass839.pdf
????PAPER??????????? 20% ?`??
?@?f??????N
?f??????????e?????
?????h??????@ 0.2 J/M2 ?????D
??????? GGA, PBE, PBE0, Hartree-Fock, HSE, B3LYP, RPBE
??????? vdW-D2, vdW-DF, vdW-DF2, SOC
?к???????????????????@ 20% ????


2.????????????????????????????????????Щ??????????????????????????????????

??????Щ????????@????M????c??????????
???īI??? ?????ó????c???????????

??????c?????????????????^??????????????N
????? lattice constant
??????? 1% ????????????
??????????????????`??
????~???????????????
??????X????????????Y??????????_????

3.????????3.5.7.9????????????????????Щ???档?????????????????????Щ??????

?@..................... ??ь??????
"??????? 3??5??7??9 ?????????? 3??5??7??9 nm ?? Al(111) ???y?Y???????@????????Щ??~~~~~"
?@??????????
9 layer Al(111) ??s 2 nm ??
??????~??????????????????? 2nm Al ??????y surface energy
????]??????????
2nm Al ?????????f????"???" ???б???
????????????"????"?????
????? 20??????????
?????????????^???
????????????? 100 ?? Al
???}??S????Q????~??????????? LDA



????~?@??īI?????]?????~??????????????~?????????]????
??????_?^ ~ ????? III. Results and discussion A. Surface properties ?????????~
??????? (?????g?????)
It is to be noted that the experimental data for the (111) surface energy are not known,
????~ 111 ???????????????]?????????????N??~???????????
and that these data in Table I refer to some (unclear?? average of several low index planes of the crystal surfaces or to liquid metals.
????????????????????????^???~?????????S????? low index surface ??Y???S????????????? Table I ?o?ゃ????
Therefore the experimental data for the surface energy should have, in general, higher values than the calculated ones.
???????? Table I ????????????????????~???????
The comparison shows that the agreement between the different theoretical results and the experimental data is good.
?????????????????????????~~~


Summary
??????????????????????īI
??S???????????@??????
??????????????????????
??????????J???@ 20% ???`??
?????B????????o??(???????????]??)??????? Al(111) surface energy ?????
10楼2013-12-13 17:46:23
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jpchou

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【答案】应助回帖

★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★
感谢参与,应助指数 +1
fzx2008: 金币+5, 谢谢指导 2013-12-09 19:05:46
otuvlh: 金币+20, ★★★很有帮助 2013-12-11 08:53:53
LZ???MS??????Al??111??????????????????????????????????
1.surface thickness?????????????????3,5,7,9?????????????????????

>  Al = face-centered cubic
    (111) surface = ABC stacking
    ?????С??С????????? ABC ?Y??(????)
    ?????????~????????±??汣?????
    ??????ζ?????????? 1
    ???????????? 3,5,7,9 ??

2.????LDA????????????????????????: ??????=??Eslab- n x Ebulk??/2A????Ebulk?????0.5*??Eslab(n+2)-Eslab??n))?????????constraint atom???о????????????ó???????????0.82J/m2???????????????е??????1J/m2????????????????????

> ?????~ ???????????
   1) LDA exchange-correlation functional ?? Al ??y???????????
   2) ????????x?????y??h
   3) too good to believe ~ ?????M(DFT level)??????o?????????c?????
       ???????`??~ ??????"???"????????"?^??????(???W)??"
       ???????????c???Y???????????~??????С??~"????"???????? >_<
2楼2013-12-09 17:48:57
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jpchou

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★ ★ ★
fzx2008: 金币+3, 谢谢指导 2013-12-13 20:21:41
"?????????????????????е?????????"

> ?e?????????? ?? ?????????
   ??o???? 1993 ?? M. Sheffler ???????īI
   ???_???????Y?????~
   ????????????~????N??????????????~??????
   ???????_?^?f??"?ó???????????0.82J/m2???????????????е??????1J/m2????"
   ???????????????? 0.82 ?????????y?? 1 ????

   ?????????V?????N?~~~~
   ?????~ ???????????
   1) LDA exchange-correlation functional ?? Al ??y???????????
       DFT ????e?汾?????????S?????? (approximation)
       ???????????Y????????????????????y??????~~
       ?@?????????y???

   2) ????????x?????y??h
       ??????? 3??5??7??9 ?????????? 3??5??7??9 nm ?? Al(111) ???y?Y?????
       ?@????????Щ??~~~~~

   3) too good to believe ~ ?????M(DFT level)??????o?????????c??????
       ???????`??~ ??????"???"????????"?^??????(???W)??"
?v???@?
??????????
"???????????????о????????е?????????????????????????????"
??rz ............
???????????īI?????e???^??? ??? ???????"???^??"?
???????]?l?F???}? ??????Мy?^ encut, kpoint, layer thickness, ???
????????]???}~???}??????????ИO????.................
8楼2013-12-12 16:54:45
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普通回帖

otuvlh

金虫 (小有名气)

引用回帖:
2楼: Originally posted by jpchou at 2013-12-09 17:48:57
LZ刚学MS,计算Al(111)面表面能时出现了以下几个问题,求高人解答:
1.surface thickness,我看文献中取的都是3,5,7,9。想问一下为什么不取偶数呢?

>  Al = face-centered cubic
    (111) surface = AB ...

承蒙指教,不胜感激。
关于计算表面能的结果,我也知道这也只是定性地说明结果,不同人做出的计算结果可能会不一样。但是,这个问题算出的结果感觉跟文献中的值差别比较大,计算方法上我也没发现什么问题。所以您说的那几个原因,窃以为本例中可能性不是很大。有没有别的方面的原因呢,关于Ebulk的取法有没有问题呢?
3楼2013-12-10 12:41:57
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jpchou

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fzx2008: 金币+3, 谢谢指导 2013-12-11 18:12:27
????????????м???
???????????????????????????????????????????????????????????????????

> ???????????????w?????????????C??
   ?Y??????????
   ?@??????????~?????????}?? (reproducible)

????????????????????о????????е????????????????????????????????????????????????????????п??????????????б????????????????Ebulk?????????????????

> http://th.fhi-berlin.mpg.de/site ... RB-48-1877-1993.pdf
  ???Y?????????
  ???????Л]??e???f????

  "??????????????????????"
   ????????"?????"?????????? ?
   ??N??"?]?l?F??N???}"?
   ??z???^????憖?}?????????Y??f  "?]?l?F??N???}"??
4楼2013-12-10 15:13:11
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otuvlh

金虫 (小有名气)

???????:
4?: Originally posted by jpchou at 2013-12-10 15:13:11
????????????м???
???????????????????????????????????????????????????????????????????

> ???????????????w?????????????C??
   ?Y??????????
   ?@?????????? ...

??????????????????????????????Al??111???????????????????????????????????????????????????????Щ???????????
?????????????????????????????????Ebulk???????Ebulk?????????????????????????????????????????3??5??7??9???5-3??7-5??9-7?????????????
5楼2013-12-11 08:53:34
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jpchou

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說真的
我不太清楚你想問什麼.................
6楼2013-12-11 16:49:21
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otuvlh

金虫 (小有名气)

引用回帖:
6楼: Originally posted by jpchou at 2013-12-11 16:49:21
說真的
我不太清楚你想問什麼.................

。。。。我想问的是为什么我做出的结果和别人的文献中的值有一点差距。。。
我之前回复您的是在说我的计算公式应该不存在什么问题,所以我想知道有没有别的原因导致计算结果与文献中的差别。
7楼2013-12-12 11:43:33
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otuvlh

金虫 (小有名气)

???????:
8?: Originally posted by jpchou at 2013-12-12 16:54:45
"?????????????????????е?????????"

> ?e?????????? ?? ?????????
   ??o???? 1993 ?? M. Sheffler ???????īI
   ???_???????Y?????~
   ????????????~????N??????? ...

??л?????????????????????????
1.?漰??????Al(111)??????????adhesion or adhesive transfer????Al??111????????????????????м?????????1J/m2???????????????????????????????????????????0.2J/M2??????20???????????????????????????????????????????????????????????????????п???????reproducible??,????????????????????????????????????e-cutoff??K-Points?????????ó??????????0.82J/m2??????????LDA??Al???????????????????????
2.????????????????????????????????????Щ??????????????????????????????????
3.????????3.5.7.9????????????????????Щ???档?????????????????????Щ??????
9楼2013-12-13 08:57:05
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