求助：请问一下IRC曲线出现多个弯，正常吗？

fuhua · 发表于 Post on 2024-11-19 20:49:22

在过渡态搜索时，找到了过渡态，但是跑IRC时发现有多个弧度，请问一下这样的过渡态是否正确？或者是IRC搜索出现了什么问题？为了查看过渡态的趋势，先用半经验方法PM6试出来的过渡态，IRC也是半经验跑出来的。是否与精度有关？

fuhua · 发表于 Post on 2024-11-19 20:51:35

%nprocshared=32
%mem=20GB
%chk=D:\G16W\Scratch\gv11_19_2024_20_50_53\Preview_ml5ej.chk
# irc=(calcfc,maxpoints=400,lqa) upm6 nosymm

Title Card Required

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sai77 · 发表于 Post on 2024-11-19 21:43:09

《在Gaussian中计算IRC的方法和常见问题》
http://sobereva.com/400
里面有类似的例子

Huschein · 发表于 Post on 7 day ago

你只是作为学习的话半经验没关系，整体趋势是对的，但是可能方法精度不高吧

sobereva · 发表于 Post on 7 day ago

中途拐弯并没有什么必然问题，通常暗示反应过程有多个stage，可以从电子结构重排/成键方式改变的角度讨论原因。但图中央过渡态位置的曲线显得很尖，如果放大了看就是个尖峰，那倒是有问题。

PM6的精度有限，不代表DFT得到的IRC曲线也能类似。如果怀疑结果，应当用DFT跑

fuhua · 发表于 Post on 7 day ago

sai77 发表于 2024-11-19 21:43
《在Gaussian中计算IRC的方法和常见问题》
http://sobereva.com/400
里面有类似的例子

好嘞十分感谢老师

fuhua · 发表于 Post on 7 day ago

sobereva 发表于 2024-11-20 05:38
中途拐弯并没有什么必然问题，通常暗示反应过程有多个stage，可以从电子结构重排/成键方式改变的角度讨论原 ...

十分感谢sob老师，我多尝试一下~

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[综合交流] 求助：请问一下IRC曲线出现多个弯，正常吗？