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小木虫论坛-学术科研互动平台 » 计算模拟区 » 量子化学 » Gaussian » 用高斯09计算的tddft方法优化激发态出现问题如何解决？
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wutongshun

金虫 (小有名气)

[求助] 用高斯09计算的tddft方法优化激发态出现问题如何解决？

用高斯09计算的tddft方法优化激发态
#p opt=maxcyc=300 td(triplets,nstates=6,root=1) b3lyp/genecp
1 3

出错信息是：
You need to solve for more vectors in order to follow this state.
Error termination via Lnk1e in /public1/soft/Gauss09/g09/l914.exe at Tue Apr 26 04:00:18 2011.
请教达人，如何解决？
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1楼 2011-04-26 11:48:06
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wutongshun

金虫 (小有名气)
引用回帖:
Originally posted by lihb734 at 2011-04-26 11:56:19:
这个问题本版回答过多次了。你自己检索能看到更详细的解答。
解决：增大nstates指定的数目
还有，你这个优化的不是T1，而是T2

怎么不是T1了？
root=1，就是T1态
我要优化的是最低激发三重态
所以自选多重=3，用的是td（triplets）
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4楼2011-04-26 12:09:21
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lihb734

铁杆木虫 (职业作家)

站在计算化学入门的门槛上

【答案】应助回帖

wutongshun(金币+1): 2011-04-26 12:08:05
这个问题本版回答过多次了。你自己检索能看到更详细的解答。
解决：增大nstates指定的数目
还有，你这个优化的不是T1，而是T2
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前途光明，出路难觅！
2楼2011-04-26 11:56:19
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pwzhou

铁杆木虫 (正式写手)

【答案】应助回帖

wutongshun(金币+1): 2011-04-26 12:40:52
引用回帖:
Originally posted by wutongshun at 2011-04-26 11:48:06:
用高斯09计算的tddft方法优化激发态
#p opt=maxcyc=300 td(triplets,nstates=6,root=1) b3lyp/genecp
1 3

出错信息是：
You need to solve for more vectors in order to follow this state.
Error termi ...

我再把Gaussian公司的回信附上来，希望这是最后一次有人问这个问题，我实在不记得这已经是多少次有人问这一个同样的问题了。问问题之前搜索一下很难吗？

In the case of "No map to state **, you need to resolve more vectors" messages, this is usually an indication that one did not include enough excited states in the TD or CIS calculation. The "States=N" option to the "TD" or "CIS" keywords tells how many excited states to include in an excited state energy calculation. If this is not specified, the default value will be "States=3". The recommended value is to include a minimum of 2 or 3 more states than the state of interest. Thus, if you want to perform a geometry optimization for excited state 5, for example, I would recommend at least using "States=7" or "States=8". The geometry optimization will be done for one excited state M, selected with "Root=M", and one has to make sure that enough states are included in the CIS or TD expansion by having "States=N" where N is larger than M.

It is possible that, at some point during an optimization of an excited state, the order of the excited states changes and the CIS or TD expansion might need to include more states in order to be able to follow correctly the state of interest. This is essentially what that message about including more vectors mean, that is that at that point, the number of states that you originally specified with "States=N" was not enough in order to solve for the state of interest, so a larger number "N" will need to be used for "States=N".

Other times, the problem is that the ground state wavefunction becomes unstable, that is one of the states that was an excited at the initial geometry now becomes lower in energy than the state that was the ground state at the initial geometry. This kind of situation, unfortunately, cannot be modeled properly with single determinant expansions such as CIS or TD, and one would need to use CAS in order to be able to deal with the conical intersection or avoided crossing of states.

Another thing to note is that one should be much more careful with geometry optimizations on excited states than for the ground state. Typically the energy differences among excited states are smaller than between the ground state and the first excited state. Thus, one can afford to perform larger geometry optimization steps when optimizing the ground state than in the case of optimizing an excited state.

A "bad" geometry optimization step in the optimization of the ground state, may take you a bit off track but in following steps the optimization might find the way back and approach the converged structure. In the case of an optimization of an excited state, a "bad" geometry optimization step will also take you off track but, since other electronic states are close in energy, it is possible that at the new geometry the order of the excited states change and now the geometry optimization follows a different electronic state.

This is not only a problem because the optimization could be pursuing a different state than the one you were interested in, but also because, if several of these changes occur during a geometry optimization, it may even be hopeless to continue with the optimization because the gradient information and the estimated hessian could be useless (since not all the previous points in the geometry optimization where points from the same potential energy surface).

As a first measure to increase the reliability of the geometry optimization of excited states, I recommend to reduce the maximum allowed step size during geometry optimizations. Try "Opt=(MaxStep=10)" to set this value to 0.10 Bohr, or a smaller value if you still have problems. The default value is typically 0.30 Bohr. Reducing the maximum allowed step size will result in the geometry optimization taking more steps to reach convergence than with the default value. This will be true obviously for well-behaved geometry optimizations, but for problematic cases it will be the other way around, i.e. it will take fewer steps (and may even be impossible with the default step size) because it will be easier for the optimizer to follow a particular electronic state if the changes from step to step are not very drastic.
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3楼2011-04-26 12:02:55
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wutongshun

金虫 (小有名气)
引用回帖:
Originally posted by pwzhou at 2011-04-26 12:02:55:
我再把Gaussian公司的回信附上来，希望这是最后一次有人问这个问题，我实在不记得这已经是多少次有人问这一个同样的问题了。问问题之前搜索一下很难吗？

In the case of "No map to state **, you nee ...

谢谢你们的帮助，不过我觉得nstates=6已经挺大了，我root=1，我只关心最低激发三重态，我又不要光谱，我只要优化的几何结构
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5楼2011-04-26 12:14:09
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