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December 12, 2019

MOPAC2012 electrostatic potential Log Out | Topics | Search
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John Keller
Unregistered guest
Posted on Wednesday, March 06, 2013 - 6:41 pm:   

Using either WebMO 12.1 or 13 (on your server), when I try to display the ESP surface using MOPAC2012 and PM6 or PM7 method, the CPU activity goes to zero when the window says "Calculating Property". PM3 works OK, however, I need the surface of an organo- metallic structure, and PM3 does not have cobalt parameters.
JR Schmidt
Moderator
Username: Schmidt

Post Number: 341
Registered: 11-2006
Posted on Thursday, March 07, 2013 - 12:57 pm:   

The problem is not PM6/PM7, but rather the presence of d-type Slater exponents. As of now, ESP cannot be calculated with d-type Slater orbitals. (d-type GAUSSIANS orbitals work fine -- but MOPAC uses STOs.)

Here is the problem: To calculate ESP efficiently, one needs a Gaussian-type basis. In a GTO basis, the electrostatic potential is a analytic function of the GTOs. This is not true with STOs, and as such, a GTO basis must be fit to the STOs. This is straightfoward for s/p functions, but much harder for d functions (since they have VERY different functional form in an STO and GTO basis.)

In summary, unfortunately, WebMO cannot do this right now. It will work just fine if you run it in an ab initio code and use WebMO!

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