[Ifeffit] Recommendations for DFT/computational chemistry software?

[Paul Fons]

Hi Scott,
	I have been dabbling in DFT for a while.  There are many free packages around, but if you would like to model XAFS as well, I would suggest an all electron code for accuracy (such as Wien2K).  For general purposes, I am also using VASP and CASTEP.  The former uses projector augmented waves and the other ultrasoft pseudopotentials.  VASP is fast and scalable to the largest machines and is designed from the ground up for quantum molecular dynamics.  Both VASP and CASTEP use pseudopotentials whereas Wien2K uses a linearized augmented plane wave basis (read as radial wavefunctions and Ylms in a sphere about each atom and plane waves between spheres with boundary condition matching at the surface of the spheres.  This way it is possible to model even the 1s electrons for heavier atoms and yes it does affect valence electron wavefunctions via orthogonality.   All of these approaches are single particle DFT approaches, but it should be good enough for a start, if you want to go beyond these, with solutions of the Bethe-Saltpeter equation (electron and a hole) things get complicated and expensive (in terms of computer time) very quickly.  

If you are interested in free software I would suggest gpaw, quantum espresso, and abinit.  I would also suggest learning the atomic simulation environment in which you can program multiple codes in python (and even solve for maximally localized Wannier functions in a few lines of code!) (Atomic Simulation Environment — ASE 3.8.0.3329 documentation).

What exactly are you trying to do?  If you are looking for a non-spherical approximation for EXAFS beyond feff8's spheres, you might try FNDMES by Joly as well.

Cheers,
		Paul


On Aug 12, 2013, at 10:30 PM, Scott Calvin <scalvin at sarahlawrence.edu> wrote:

> Hi all,
> 
> I know many of you use DFT calculations to help model EXAFS data for molecular compounds. Do you have recommendations for good computational chemistry packages, commercial or otherwise, to use for that purpose? 
> 
> --Scott Calvin
> Sarah Lawrence College
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Dr. Paul Fons
Chief Senior Research Scientist
Functional Nano-phase-change Research Team
Nanoelectronics Research Institute
National Institute for Advanced Industrial Science & Technology
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