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友风

铁虫 (小有名气)

[交流] [求助]找过渡态为什么老是出错呢!求高手帮忙!

我在做一个CH4+O2反应的过渡态,其实就是O2夺氢;由于是新手,先用QST2方法找,出现了L9999的错误;我看结构还合适,取出最后一步,采用TS优化,可是还出现L9999错误;其实我已经加到maxcycle=300了,看了中间说Wrong number of Negative eigenvalues: Desired=  1 Actual=  2
后又加入(modredundant,noeigen)但是又出现了不收敛,而且结构也偏离的我向要的。
氢高手帮帮忙!我用的是b3lyp/6-311++g(d,p)
非常感谢!
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虚谦

至尊木虫 (正式写手)

★ ★
友风(金币+1,VIP+0):zz
zzgyb(金币+1,VIP+0):谢谢你的参与,欢迎再次光临计算模拟版!
999不是错误
是在你规定的步数内没有走完
接着再算就可以
不过你优化过渡态的话出现502不收敛的情况就调整结构吧
一般没有别的好办法
大家都说我是个好人,其实,我也是这么想的~!
2楼2008-11-12 19:33:59
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友风

铁虫 (小有名气)

引用回帖:
Originally posted by 虚谦 at 2008-11-12 19:33:
999不是错误
是在你规定的步数内没有走完
接着再算就可以
不过你优化过渡态的话出现502不收敛的情况就调整结构吧
一般没有别的好办法

但是我已经加到了300步,甚至500步了。
3楼2008-11-12 20:01:15
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虚谦

至尊木虫 (正式写手)


zzgyb(金币+1,VIP+0):谢谢你的参与,欢迎再次光临计算模拟版!
你可以把最后的结构提出来再次优化
大家都说我是个好人,其实,我也是这么想的~!
4楼2008-11-13 10:06:19
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lb1586551

铜虫 (小有名气)


zzgyb(金币+1,VIP+0):谢谢你的参与,欢迎再次光临计算模拟版!
If you want to find out the right transition state, you are of only necessity to change the initial guess. The other methods are only secondary.
5楼2008-11-13 15:03:24
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友风

铁虫 (小有名气)

引用回帖:
Originally posted by lb1586551 at 2008-11-13 15:03:
If you want to find out the right transition state, you are of only necessity to change the initial guess. The other methods are only secondary.

谢谢,我也调了;这个体系本来就很小,过渡态该比较好找。可是老是找不到。调了之后我都用了这样的方法还是不行,算了将近2小时,以link9999告终。
#gfinput iop(1/8=2)                                                               
#UB3lyp/6-311g opt=(ts,noeigen,calcFC,maxcycle=300) freq scf=(maxcycle=500) test
请问我还可以怎么整啊?谢谢!
6楼2008-11-17 16:00:38
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lb1586551

铜虫 (小有名气)

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spur(金币+2,VIP+0):^_^ Many thanks!!Welcome to emuch!
I have to admit that there are several reasons that can lead to the difficulties of calculated transition state. First, due to the b3lyp/6-311++G(d.p), it is likely that you can not seek for the transition state for the specific reaction. I suggest that you may use other methods such as MP2, BHandHLYP and so on. Second, What is worse, it is of great possibility that there is no transition state existed.
7楼2008-11-17 17:00:08
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友风

铁虫 (小有名气)

引用回帖:
Originally posted by lb1586551 at 2008-11-17 17:00:
I have to admit that there are several reasons that can lead to the difficulties of calculated transition state. First, due to the b3lyp/6-311++G(d.p), it is likely that you can not seek for the tr ...

thank you very much !
1.i am trying to find the TS of such a reaction : H abstraction .
  CH4 +O2=CH3+HO2
and it is proved that a transtion state exists and somebody found it with b3lyp .
2.i am a rookie now .but i tried TS and qst2 .but it always ended with the errors i mentioned above .
3.i tried changing or adding key words ,and chang ing the initial geom,but it did not work either .this makes me very frustrated and a little anxious .
so ,i am here to ask all you for help !
thank you all !

[ Last edited by 友风 on 2008-11-17 at 19:41 ]
8楼2008-11-17 19:29:05
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hanjunfeng

银虫 (小有名气)


lei0736(金币+1,VIP+0):谢谢
用QST3试试
OK
9楼2008-11-24 09:43:29
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gaochao85

铜虫 (正式写手)

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lei0736(金币+2,VIP+0):谢谢 欢迎光临
I think you should build the reactnat complex firstly. second, "opt" the complex.
and then use QST2
10楼2008-11-24 11:33:29
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