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FIZIKA A 17 (2008) 3 , 87-102
 
LATTICE DYNAMICS OF EQUIATOMIC BINARY ALLOYS
ADITYA M. VORA
Parmeshwari 165, Vijaynagar Area, Hospital Road, Bhuj - Kutch, 370 001, Gujarat, India
Tel.: +91-2832-256424, E-mail address: voraam@yahoo.com
Received 3 November 2006; Revised manuscript received 1 March 2008
Accepted 3 December 2008 Online 28 January 2009
In the present article, the calculations of the lattice dynamical properties of
four equiatomic binary alloys viz. Na0.5Li0.5, Na0.5K0.5,
Na0.5Rb0.5
and Na0.5Cs0.5 to second order in local model potential is
discussed in terms of real-space sum of Born von Karman central force constants.
Well known Ashcroft's empty core (EMC) model potential has been used to study
the lattice dynamical properties. Instead of the average of the force constants
of metallic Li, Na, K, Rb and Cs, the pseudo-alloy-atom (PAA) is adopted to
compute directly the force constants of four equiatomic sodium-based binary
alloys. The exchange and correlation functions due to Hartree (H) and
Ichimaru-Utsumi (IU) are used to investigate influence of screening effects.
Results for the lattice constants i.e. C11, C12, C44,
C12-C44, C12/C44 and bulk modulus (B) obtained
using the Hartree screening function have higher values in comparison with the
results obtained for the same properties using Ichimaru-Utsumi (IU) screening
function. The results for the shear modulus (C¢), deviation from Cauchy's relation (C12/C44), Poisson's
ratio (s), Young modulus (Y), propagation velocity of elastic waves, phonon dispersion
curves and degree of anisotropy (A) are encouraging for the four equiatomic
Na-based binary alloys.
PACS numbers: 63.50.+x, 62.30.+d, 62.20.-x, 62.20.Dc
UDC 538.911, 539.32
Keywords: lattice dynamics, lattice dynamical properties, sodium-based
equiatomic alloys
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