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#1 2017-09-11 13:47:46

I_was_a_baby
Member
Registered: 2017-09-11
Posts: 29

A comparison of several atomic charge methods in water molecule

by I_was_a_baby

As an extremely powerful program for realizing electronic wavefunction analysis, Multiwfn also can be applied to calculate the atomic charges of each atoms in molecule. Currently, the CM5 method, charge Model 5 by D. G. Truhlar, has been supported by Multiwfn. It can be seen that, from the definition, the CM5 method is a correction for Hirshfeld charge, just like the ADCH charge by Lu Tian.

It makes me pay more attention on the difference between them. So, by taking a water molecule as examples, there are some atomic charges have been obtained as list below. The level of geometry optimization is B3LYP/6-311G*.


Hirshfeld
1(O ) is   -0.328822
2(H ) is    0.164430
3(H ) is    0.164430
ADCH
1(O ) is   -0.812445
2(H ) is    0.406242
3(H ) is    0.406242
CM5
1(O ) is   -0.661055
2(H ) is    0.330546
3(H ) is    0.330546
AIM
1(O ) is   -1.027696
2(H ) is    0.513844
3(H ) is    0.513852


There is a obvious finding that the correction of ADCH charge for Hirshfeld charge is in excess of that of CM5 charge. So, if the regular calculation can be done, the ADCH charge can be recommended.

On the other hand, the AIM charge has been overrated the atomic charge. As the same as the cost contained time and computing resource is high, the AIM method for atomic charge is not suggested.

Last edited by I_was_a_baby (2017-09-11 13:48:23)

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#2 2017-09-11 13:56:15

muxijiao
Member
Registered: 2017-09-11
Posts: 1

Re: A comparison of several atomic charge methods in water molecule

why the charge of 2(H ) and 3(H ) in AIM are inequality?

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#3 2017-09-11 14:06:49

I_was_a_baby
Member
Registered: 2017-09-11
Posts: 29

Re: A comparison of several atomic charge methods in water molecule

I believe it must be a numerical error by generating integral of AIM basin of each atoms. When the AIM basin of each atoms has been calculated, the symmetry of system can be ignored.

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#4 2017-09-11 22:01:04

sobereva
Tian Lu (Multiwfn developer)
From: Beijing
Registered: 2017-09-11
Posts: 1,639
Website

Re: A comparison of several atomic charge methods in water molecule

I_was_a_baby wrote:

by I_was_a_baby

There is a obvious finding that the correction of ADCH charge for Hirshfeld charge is in excess of that of CM5 charge. So, if the regular calculation can be done, the ADCH charge can be recommended.

On the other hand, the AIM charge has been overrated the atomic charge. As the same as the cost contained time and computing resource is high, the AIM method for atomic charge is not suggested.

I totally agree with you.

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#5 2017-09-11 22:03:37

sobereva
Tian Lu (Multiwfn developer)
From: Beijing
Registered: 2017-09-11
Posts: 1,639
Website

Re: A comparison of several atomic charge methods in water molecule

muxijiao wrote:

why the charge of 2(H ) and 3(H ) in AIM are inequality?

For highly symmetric system like benzene, the inequality problem will be more evident. The essential reason is that the basin module is based on cubic grid, however, the grid distribution commonly does not conform to molecular symmetry.

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