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gujing136

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[求助] 请教各位大侠,高斯技术部的回复。控制电子排布轨道的具体操作如何执行?

F: In my  research,I  expect to allocate certain electron to assigned orbitals.  But I'm not sure G09 can  do it, and if can, how to set the  keywords?

A:There are a couple of different ways people like to think about placing electrons and most of them are inconsistent with SCF methods which are solving the electronic wavefunction for the lowest energy and often undoes any attempt to place electrons.
The cases where you can do this are when you have different spin or space symmetry.  So you can always do the lowest singlet and triplet energies because they are orthogonal by spin symmetry.  Similarly if your molecule has symmetry you can make different triplets.  Finally in some cases it is possible to build up localized spin states which are stable.  We have a worked example at our web site,
www.gaussian.com/g_tech/afc.htm
which does this for a binuclear metal system.
The Guess=(Read,Permute) keyword option is what you can use for simple witches of occupation.  Run a preliminary calculation and then you can use GaussView to identify the orbitals.  GaussView will let you drag electrons between orbitals and then make the input using Guess=(Read,Permute) to switch them in the initial guess.  The Guess=Fragment approach is detailed in the white paper above and can be used for more complex cases.
Please review these options and let me know if you have more questions.
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mchen10

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gmy1990(金币+3): 2011-12-11 14:56:22
先算一个 guess(only) pop(full)得到高斯默认的初始排布

再用guss(alter) 或 guess(permute)改变排布

注意,很多时候即使改变了初使排布,也不一定能在最终结果中得到需要的电子排布。程序只能给出 某个”态“ (比如说: singlet A1g) 的最稳定的电子排布。所以高对称性的分子更容易控制轨道电子排布
更痛苦的是梦没醒路已经不能走了
2楼2011-12-11 14:23:48
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beefly

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用了Guess(Alter)以后,如果组态在SCF过程中仍发生改变,可以加上选项IOp(5/15=2),使每个不可约表示的占据数在轨道交换后保持不变。但是这个选项仅对阿贝尔点群(D2h及其子群)有效。
beefly《西太平洋大学现代英汉词典》[bi:fli]牛肉一般地
3楼2011-12-12 00:42:38
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gujing136

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引用回帖:
: Originally posted by mchen10 at 2011-12-11 14:23:48:
先算一个 guess(only) pop(full)得到高斯默认的初始排布

再用guss(alter) 或 guess(permute)改变排布

注意,很多时候即使改变了初使排布,也不一定能在最终结果中得到需要的电子排布。程序只能给出 某个”态 ...

请问大侠,如何只算初始排布呢?
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4楼2011-12-14 14:57:47
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zhangmt

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【答案】应助回帖

感谢参与,应助指数 +1
Gaussion03 中文用户手册,第99-100页,对用Guess=only获取初始猜,然后用guess=alter重排分子轨道有清晰的描述和实例,请认真研读。另外101页还给出了如果不用guess=alter而用guess=permute的方式打乱整体分子轨道的用法实例。
一群自以为正义凛然的年轻人将一切不能以科学解释的事情定性为封建迷信并大刀阔斧地进行消灭,其实这是修养不足学识浅薄的一种体现,也是可恶的偏执和愚蠢的自以
5楼2011-12-14 16:52:03
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