Questions tagged [semi-empirical-method]
The semi-empirical-method tag has no usage guidance.
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Why is INDO suitable for covalent systems despite neglecting two-center two-electron integral?
I do not have a good basis understanding of basic chemistry so I am hoping to obtain an explanation that is as narrow as possible.
My current understanding of the semi-empirical method INDO is that
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Using 3 layer ONIOM(M06-2X:PM7:UFF) over 2 layer ONIOM(M06-2X:AMBER) or 2 layer ONIOM(M06-2X:OPLS) to study enzymatic aldehyde reduction
I'm trying to model the reaction mechanism of an enzymatic steroid reduction. Experimental research proposes a large variety of intermediates, which I believe would each require separate ...
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Which quantum chemistry approximation to use?
I'm just getting started with quantum chemistry using some simple test problems. I have a few of the software packages installed (ASE, Psi4, GPAW etc) and everything is working - no issues with the ...
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How to create a Potential Energy Surface in Chemcraft?
The Chemcraft website says that it is possible to create a potential energy surface. Nevertheless, it doesn't work for my Gaussian scan job.
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I'd like to model some compounds with DFTB, but some elements don't have parameter files in the official site. Is there a workaround?
I was reading a bit about this technique, Density Functional based Tight binding (DFTB). It's claimed it can provide a speed improvement of several fold when compared to plain DFT, still giving ...
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MNDO integrals in the global coordinate system
In MNDO and its descendants (Sewart's PMx models, Austin's AM1, MNDO/d, etc.), the nonvanishing two-center two-electron "coulomb integrals" are evaluated via a classical multipole expansion in a local ...
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Are there Exchange integrals in Semiempirical methods?
One of the major features of semiempirical methods is that they significantly reduce the cost of evaluating 2-electron integrals.
In general, they follow the formula for HF, but, introduce many ...
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Are there any semiempirical methods that work with heavy alkaline earth metals?
I did some research. Found some semiempirical methods that work even with heavy lanthanide compounds (RM1). But could not find any references to semiempirical methods compatible with the heavier ...
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CNDO/2 clarification
I wrote a piece of code on RHF using Python a while back, and figured I'd extend it to also implement CNDO/2 (yes, I know it's old but I figured it'd be easier for me.)
The approximated Fock matrix ...
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