Effective Medium Theory (EMT) model based on the EMT implementation in
ASAP (https://wiki.fysik.dtu.dk/asap).  This model uses the asap_emt_driver
model driver.

Effective Medium Theory is a many-body potential of the same class as Embedded
Atom Method, Finnis-Sinclair etc.  The main term in the energy per atom is the
local density of atoms.

The functional form implemented here is that of Ref. 1.  The principles behind
EMT are described in Refs. 2 and 3 (with 2 being the more detailed and 3 being
the most pedagogical).  Be aware that the functional form and even some of the
principles have changed since refs 2 and 3.  EMT can be considered the last
step of a series of approximations starting with Density Functional Theory,
see Ref 4.

This model implements the "official" parametrization as published in Ref. 1.


REFERENCES:

[1] Jacobsen, K. W., Stoltze, P., & Nørskov, J.: "A semi-empirical effective
medium theory for metals and alloys". Surf. Sci. 366, 394–402  (1996).

[2] Jacobsen, K. W., Nørskov, J., & Puska, M.: "Interatomic interactions in
the effective-medium theory". Phys. Rev. B 35, 7423–7442 (1987).

[3] Jacobsen, K. W.: "Bonding in Metallic Systems: An Effective-Medium
Approach".  Comments Cond. Mat. Phys. 14, 129-161 (1988).

[4] Chetty, N., Stokbro, K., Jacobsen, K. W., & Nørskov, J.: "Ab initio
potential for solids". Phys. Rev. B 46, 3798–3809 (1992).


KNOWN ISSUES / BUGS:

* This implementation does not support ghost atoms,
  i.e. numberContributingParticles must be equal to numberOfParticles.  If
  this is not the case, the ghost atoms are not handled the way OpenKIM
  expects, and forces would be wrong.  The model initialization therefore
  fails if numberContributingParticles != numberOfParticles and the model 
  declares it wants to calculate forces.
  In the long run, this should be fixed in Asap.  For more info, see
  https://trac.fysik.dtu.dk/projects/Asap/ticket/48

* On-the-fly modifications of the parameters is not supported.  It should be
  implemented.

* More testing is needed.

All URLs refer to the TRAC bug handling system of ASAP.  You can check there
if the issues have been addressed.


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