[Pw_forum] Finding effective mass

[Eduardo Ariel Menendez Proupin]

Dear Padmaja,
Quantum ESPRESSO calculates the band energies by a method different from
k.p. If you want to calculate an effective mass you can use QE to calculate
the band energies in the neighborhood of the desired k-point and then obtain
the effective mass doing numerical derivation.

If you want to get inside he code, you can extract the matrix elements of
the momentum operator and program the calculation of the effective mass.

Due to the non-locality of the pseudopotentials, as well as of the GGA
functionals, I am not sure if the expressions found in the  50's classic
papers (e.g. Kohn&Luttinger) can be applied. In presence of non local
hamiltonian it is not true that p/m=[H,r]/ihbar
 I know that  for optical properties, the momentum operator in the A.p
interaction hamiltonian has to be replaced by a generalized operator. See,
e.g., PRB48, 11789 (1993) and PRB 73, 045112 (2006). Hence, I suspect you
would have to repeat the derivation made in the classic papers, or find
where it is done (and let me know your findings).

Best regards
Eduardo

---------- Mensaje reenviado ----------
From: Padmaja Patnaik <padmaja_patnaik at yahoo.co.uk>
To: "pw_forum at pwscf.org" <pw_forum at pwscf.org>
Date: Tue, 27 Sep 2011 07:24:52 +0100 (BST)
Subject: [Pw_forum] Finding effective mass
Dear All

Is it possible to calculate effective mass using k.p method in quantum
espresso?



-- 


Eduardo Menendez Proupin
Departamento de Química Fisica Aplicada
Facultad de Ciencias
Universidad Autónoma de Madrid
28049 Madrid, Spain
Phone: +34 91 497 6706

On leave from: Departamento de Fisica, Facultad de Ciencias, Universidad de
Chile URL: http://fisica.ciencias.uchile.cl/~emenendez

"*Padece, espera y trabaja para gentes que nunca conocerá y que a su vez
padecerán, esperarán y trabajarán para otros, que tampoco serán felices,
pues el hombre ansía siempre una felicidad situada más allá de la porción
que le es otorgada. Pero la grandeza del hombre está precisamente en querer
mejorar lo que es. En imponerse Tareas. En el Reino de los Cielos no hay
grandeza que conquistar, puesto que allá todo es jerarquía establecida,
incógnita despejada, existir sin término, imposibilidad de sacrificio,
reposo y deleite. Por ello, agobiado de penas y de Tareas, hermoso dentro de
su miseria, capaz de amar en medio de las plagas, el hombre puede hallar su
grandeza, su máxima medida en el Reino de este Mundo*".
Alejo Carpentier, El reino de este mundo, (1949).

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