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May 25, 2019

Gaussian Single Occupancy of MOs Log Out | Topics | Search
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Cody Fagan
Unregistered guest
Posted on Tuesday, September 02, 2014 - 11:37 am:   

When I attempt to run a MO calculation with the gaussian engine, I consistently get single occupancy in each MO no matter what the basis set/ theory used. Any known sources of this issue or fixes ?
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JR Schmidt
Moderator
Username: Schmidt

Post Number: 412
Registered: 11-2006
Posted on Tuesday, September 02, 2014 - 11:41 am:   

This is probably NOT a bug. Rather, you are probably running a molecule that is not a singlet (odd number of electrons, etc.) In that case the calculation runs with an "unrestricted" reference, giving different sets of alpha/beta spin orbitals, each singly occupied.
Cody Fagan
Unregistered guest
Posted on Tuesday, September 02, 2014 - 1:47 pm:   

I am still experiencing the same issue even when changing the multiplicity. I get a non answer for odd multiplicity (which makes sense) I am attempting to run it on a transition metal [Cu(Cl6)]4- would that add to any issues ?

*this is my first computational project so I am learning as I go, and and all advice is extremely appreciated*
JR Schmidt
Moderator
Username: Schmidt

Post Number: 413
Registered: 11-2006
Posted on Tuesday, September 02, 2014 - 2:04 pm:   

Your complex has an odd number of electrons. It CANNOT be a singlet. This is not a bug. I would recommend "Introduction to Computational Chemistry" by Jensen for a simple primer.
Cody Fagan
Unregistered guest
Posted on Tuesday, September 02, 2014 - 2:23 pm:   

It was set to a doublet when I noticed the single occupancy, I was not attempted it as a singlet which you keep referencing to. The single occupancy still occurs for any even multiplicity I set it too.

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