[Ifeffit] Debye model on Artemis

[Frenkel, Anatoly]

Kleber,
 
Correlated Debye Model (CDM) was proposed by Sevillano, Meuth and Rehr in 1979 in a Phys Rev B artcile. It also shows how to find sigma2(T) from the CDM- and also from Einsten model, by the way. In the former case, you take phonon density of states in Debye approximation (where it is proportional to the square of the mode frequency) and projoect it on the direction of the bond between the atoms, so the modified projected density of states is used to calculate vibrational amplitudes. Similarly, it can be used to calculate not vibrational amplitudes but third cumulant but it has not been done with CDM to my knowledge. It was done only for the Einstein moedl in the subsequent papers though, as you and Bruce wrote.
 
Anatoly
 
 

________________________________

From: ifeffit-bounces at millenia.cars.aps.anl.gov on behalf of Kleber Daum Machado
Sent: Wed 5/12/2010 1:59 PM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: [Ifeffit] Debye model on Artemis



Hi Matt,

Concerning the third cumulant, my problem is to use a particular model
for it. Some articles (Frenkel and Rehr, PRB 48 (1993) 585; Araujo et
al, PRB 74 (2006) 184102) show how to use the Einstein model on Artemis,
since these articles show the expressions that should be defined for
sigma^2(T) and C3(T) for this model in Artemis (eqs. 11 and 18 of
Frenkel and eqs. 2 and 3 of Araujo). In fact, I have already tested them
on my analysis, using the eins function for sigma^2 and defining the
C3(T) expression given in those articles in Artemis. I'd like to test
Debye model too, and my problem is to use Debye model for sigma^2(T) and
C3(T). For sigma^2(T) Artemis has the debye function already predefined.
I'd like to use/write an expression for C3(T) considering Debye model,
but I didn't find anything about such expression on the literature.

Kleber
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