[ase-users] ASAP and EMT calculator

[Jakob Schiøtz]

Dear Amanda,

The EMT model assumes that there is no directional bonding, for this reason it only works for elements that crystallize in a closed-packed structure.  In particular, it works well for the late transistion metals with a full d-band.  It is likely to be possible to fit parameters to other closed packed metals, but it requires some work.  I am looking at refitting parameters with a student, we could eventually try to include Ti in the fitting.

You can read more about EMT in these papers:

K.W. Jacobsen.  Bonding in metallic systems: An Effective-Medium approach. Comments Cond. Mat. Phys. (1988) vol. 14, No. 3 pp 129-161.
K.W. Jacobsen et al. A semi-empirical effective medium theory for metals and alloys. surface science (1996) vol. 366 (2) pp. 394-402
Chetty et al. Ab initio potential for solids. Phys. Rev. B (1992) vol. 46 (7) pp. 3798-3809

The first explains the principles behind EMT in a pedagogical manner.  The second documents the current form of the potential, it has changed significantly since the first paper.  The third demonstrates how EMT can be derived from DFT through a chain of approximations.

I hope this helps

Jakob


On 7 Apr, 2011, at 19:26, Amanda Stott wrote:

> Dear ASE Users, 
> 
> Could someone point me in the direction of a few papers which explain the implementation of the EMT and ASAP calculators? I was wondering how/why the elements Ni, C, Pt, Ag, H, Al, O, N, Au, Pd, Cu were chosen. If I wish to use ASE to calculate phonon modes of Ti, for example, would I need to do to implement Ti into the EMT calculator? I know the given elements are parameterized in EMT.py but I am sure there is more to it than that. Any help on this matter would be greatly appreciated. 
> 
> Best Regards, 
> 
> -- 
> Amanda Stott
> Graduate Research and Teaching Assistant
> The University of Alabama
> Department of Chemistry
> Tuscaloosa, AL 35487-0336
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--
Jakob Schiøtz, Ph.D.
Associate professor (lektor)
Study leader, M.Sc. in Physics and Nanotechnology
(kandidatstudieleder, Fysik og Nanoteknologi)
CINF, Department of Physics
Technical University of Denmark
DK-2800 Kongens Lyngby, Denmark
http://www.cinf.dtu.dk/~schiotz/