Commun. Comput. Phys., 15 (2014), pp. 556-568.


Vibrational Properties of Vacancy in Na and K Using MEAM Potential

Vandana Gairola 1*, P. D. Semalty 1

1 Department of Physics, H N B Garhwal University Campus, Badshahithaul Tehri Garhwal - 249199, India.

Received 9 January 2013; Accepted (in revised version) 7 August 2013
Available online 8 October 2013
doi:10.4208/cicp.090113.070813a

Abstract

The modified embedded atom method (MEAM) with the universal form of embedding function and a modified energy term along with the pair potential has been employed to determine the potentials for alkali metals: Na, K, by fitting to the Cauchy pressure $(C_{12}-C_{44})/2$, shear constants $G_v=(C_{11}-C_{12}+3 C_{44})/5$ and $C_{44}$, the cohesive energy and the vacancy formation energy. The obtained potentials are used to calculate the phonon dispersions of these metals. Using these calculated phonons we evaluate the local density of states of neighbours of vacancy using Green's function method. The local density of states of neighbours of vacancy has been used to calculate mean square displacements of these atoms and formation entropy of vacancy. The calculated mean square displacements of both 1st and 2nd neighbours of vacancy are found to be lower than that of host atom. The calculated phonon dispersions agree well with the experimental phonon dispersion curves and the calculated results of vacancy formation entropy compare well with the other available results.


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PACS: 61.72.jd, 61.72.S, 63.20D
Key words: Embedded atom method (EAM), modified embedded atom method (MEAM), Green's function, force-constants, vacancy, phonon dispersion, local density of states, mean square displacement, formation entropy.

*Corresponding author.
Email: vandanagairola@hotmail.com (V. Gairola), semalty@rediffmail.com (P. D. Semalty)
 

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