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小木虫论坛-学术科研互动平台 » 计算模拟区 » 计算模拟 » 【讨论】TD-DFT计算电子光谱请教高手，如何回答审稿人问题
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brilliant

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[交流] 【讨论】TD-DFT计算电子光谱请教高手，如何回答审稿人问题

The experimental work is supported by by theoretical DFT calculation using Gaussian software.Calculations confirmed stability of determined structure. Authors also calculated UV-Vis spectra by means of TDDFT and conclude that experimentally observed spectrum is in good agreement with calculated one. At this point I do not agree with the claim that calculation agrees well with experiment, but, understandably, more precise calculation (e.g. by means of GW and Bethe Salpeter equation) is too demanding for such large system. Experimentally unobserved peaks in calculated spectra are of the same intensity as observed one, thus natural question is if the calculated oscillator strength is overestimated for the peaks at 449nm and 374nm or the problem is more deep due to some TDDFT deficiency (e.g. HOMO-LUMO gap underestimate) and both peaks positions and also intensities are in question. I would welcome if the authors can comment this point.

[ Last edited by brilliant on 2010-3-10 at 06:52 ]
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1楼 2010-03-08 06:49:26
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beefly

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brilliant(金币+5):谢谢 2010-03-08 13:48
mingdong(金币+1):感谢交流！ 2010-03-08 23:14
似乎含有过渡金属。是什么金属？用的什么泛函？
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beefly《西太平洋大学现代英汉词典》[bi:fli]牛肉一般地
2楼2010-03-08 13:27:31
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brilliant

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fegg7502(金币+1):鼓励交流 2010-03-09 16:25
The gas phase geometry of the  铜  complex  was optimized without any symmetry restriction in the doublet state with the DFT method using the hybrid B3LYP functional of GAUSSIAN-03. The calculation was performed by using the standard 6-31G* basis set for C, H, N, and O atoms, and effective core potentials basis set of LanL2DZ for Cu atom

铜配合物

[ Last edited by brilliant on 2010-3-8 at 13:49 ]
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3楼2010-03-08 13:47:35
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c111999

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dongdong3881(金币+1):多谢交流 2010-03-09 13:33
brilliant(金币+15):thanks 2010-03-09 13:40
这是实验问题，为什么704的锋能识别，别的（628~374）识别不了？
希望你给的表是用作supporting material
计算值很难完全跟实验值重合：容积效应（温度，熵，电子绳子耦合……），DFT本身的问题。你只能强调最强的两个锋算出来了。

We appreciate the reviewer's comments on some calculated but experimentally unresolved peaks (449 and 374). Oscillator strength may be overstimated in the gas phase than in the solution, i.e. we calculated gas phase molecule, which approximately represents solution result. It is known solution will reduce transition intensity. However, the calculations do capture the major transition peaks, which are also oberved experimentally. In this sense we say the calculations agree with experiments well.
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4楼2010-03-09 11:25:23
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beefly

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小木虫(金币+0.5):给个红包，谢谢回帖交流
fegg7502(金币+1):thank you very much! 2010-03-09 16:26
过度金属的激发能受杂化泛函精确交换项的影响可能会比较大，特别是对开壳层分子。建议用纯GGA如BLYP重算一次激发能，和B3LYP比，看看激发能或HOMO-LUMO gap差多少。
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beefly《西太平洋大学现代英汉词典》[bi:fli]牛肉一般地
5楼2010-03-09 13:50:56
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brilliant

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非常感谢beefly老师和c111999  

TD-DFT is a formally exact theory that relies on the analysis of the time-dependent linear response of the formally exact ground-state density to a time-dependent external perturbation, which after Fourier transformation yields exact excited-state energies and oscillator strengths. The derivation of the famous Runge-Gross theorem and the subsequent formulation of a time-dependent Kohn-Sham equation were the cornerstones in the development of the TD-DFT formalism. However, since the exact xc functional is not known, approximate xc functionals need to be employed in a practical calculation. Usually the adiabatic local density approximation (ALDA) is employed, and standard time-independent xc functionals derived for ground-state DFT are used. Concomitantly, errors in the excitation energies and oscillator strengths are introduced.

[ Last edited by brilliant on 2010-3-10 at 06:56 ]
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6楼2010-03-10 06:55:11
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c111999

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小木虫(金币+0.5):给个红包，谢谢回帖交流
luoqiquan(金币+1):ths 2010-03-10 16:43
你这些都是废话,千万别说这是你给编辑的回信里的内容
关键是你们声称计算结果与实验符合的很好，是不准确的。
必须强调气相计算模型与溶液中的试验是不一样的，所以结果也不一样。

[ Last edited by c111999 on 2010-3-10 at 11:37 ]
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7楼2010-03-10 11:33:56
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beefly

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小木虫(金币+0.5):给个红包，谢谢回帖交流
luoqiquan(金币+2):thank you 2010-03-11 18:19
TDDFT不符合实验结果主要原因有：1. 多参考体系，2. 多电子激发，3. 强关联。

对于可见光区和近红外区的价激发态来说，2一般可以忽略。

判断3的一个简单办法是比较杂化泛函（如B3LYP）和纯泛函（如BLYP）的tddft激发能或homo-lumo gap。二者若相差不大，则不属于强关联。如果是强关联，则需要另外找一个精确交换比较合适的杂化泛函（类似于GGA+U中的调节U参数）。

如果是第1的情况，tddft做不了。
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beefly《西太平洋大学现代英汉词典》[bi:fli]牛肉一般地
8楼2010-03-11 00:34:47
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