Questions tagged [semi-empirical-method]

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4
votes
1answer
60 views

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 ...
2
votes
0answers
34 views

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. ...
12
votes
0answers
168 views

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 ...
3
votes
1answer
63 views

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 ...
6
votes
1answer
108 views

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 ...
6
votes
1answer
86 views

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 ...
3
votes
0answers
49 views

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 ...