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zdhlover

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[交流] 【求助】期待高人回答掺杂建模时如何建立√2×√2×2的超胞？

在做掺杂建模计算时候如何建立√2×√2×2的超胞？为什么要建立这种超胞？建立这类超胞的原则是什么？希望高人给予解答

另外顺路问两个问题：1；在构造一个√3×√3的pt（111）表面U、V选取的原则？也就是U、V满足什么样的方向性和数值是如何确定的？
2；在某个面上选取一个√2×√2×R45度的周期性之类胞的原则是怎么样确定的？

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zdhlover(金币+4,VIP+0):谢谢你的热情回答，欢迎常理 6-16 02:38

在做掺杂建模计算时候如何建立√2×√2×2的超胞？为什么要建立这种超胞？建立这类超胞的原则是什么？希望高人给予解答
1.
√2= √2*distance between two nearest atoms in the same surface
√2×√2×2 means lattice vector a,b,c=√2,√2, 2 (2*distance between two layers)
You can draw such a box in the solid, in the box you will have atoms, which is the supercell.
2.
This is a way to a) generate certain fractional coverage on the surface, b)reduce the calculation time. e.g. if you have one atom absorbed on top of this √2×√2×2 supercell, you will have 1/2ML. This is much smaller (faster in CPU time) than if you have 2x2x2 supercell, you need 2 atoms to be absorbed on top of it to generate a 1/2ML.
3.
Try to reduce computational expense as much as possible by making use of non-integral sized supercell;
Try to generate special coverage (1/3, 1/5....).
The price you may pay for such supercells is the limited way to arrange absorption position, because you've reduced the supercell to some optimal size.

另外顺路问两个问题：1；在构造一个√3×√3的pt（111）表面U、V选取的原则？也就是U、V满足什么样的方向性和数值是如何确定的？
U.V you mean a,b (approx. x,y) vectors in the same surface?
If so, the directions of them follow the most densely packed direction of atoms (distance between two adjacent atoms is the smallest). For Pt 111, U,V should have 60 or 120 degree.
The amplitude of U,V are limited by your requirement of surface absorption requirement. E.g. you want a 1/4ML, you should have at least 2x2 surface with one absorption site.
2；在某个面上选取一个√2×√2×R45度的周期性之类胞的原则是怎么样确定的？
Sorry, do not understand this R45. If this is the angle between two surface vectors (√2×√2), then it means the way of packing is different from other surface. Just a guess.

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