Questions tagged [semi-empirical-method]

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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 ...
Physkid's user avatar
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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 ...
Runa's user avatar
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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 ...
Alex I's user avatar
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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 ...
ANZGC FlyingFalcon's user avatar
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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 ...
ksousa's user avatar
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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 ...
ANZGC FlyingFalcon's user avatar