Temperature and pressure dependent structural, electronic and thermodynamic characterization of isotypic intermetallics: LaMgX (X 5 Ga, In, Tl)

R P Singh*

 Department of Physics, S. S. V. College, Hapur, U. P., India

 Received: 07 June 2014 / Accepted: 20 August 2014

Abstract:

The full-potential linear augmented plane wave plus local orbital method has been used to study the structural, electronic and thermodynamic properties of LaMgX (X = Ga, In, Tl). The equilibrium structural properties viz. lattice parameters (a0, c0), bulk modulus (B0) and its first order pressure derivative (B0 0) have been calculated in the parent hexagonal P-62m phase. The electronic behavior has been shown in terms of band structure and density of states histograms, indicating dominant character of ‘‘5d’’ orbital electrons of Tl in electronic contribution to LaMgTl. Effects of temperature and pressure on unit cell volume (V), bulk modulus (B), Debye temperature (hD), Gru¨neisen parameter (c), specific heat (CV) and thermal expansion coefficient (a) have been investigated in wide temperature range and pressure range. The calculated parameters are in good agreement with available experimental/theoretical literature values.

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2. Computational approach

First principle structural, electronic and thermodynamical calculations based on density functional theory (DFT)  implemented in WIEN2k and Gibbs2 packages were investigated for LaMgX (X = Ga, In, Tl) intermetallic compounds [15, 16]. The advanced full potential linearize augmented plane wave plus local orbital (FP-LAPW ? lo) method [17] was used to linearize the energies, i.e., highly accurate technique based on DFT. For structural and electronic properties, linearized gradient approximation (GGA) was used [18]. The k and E convergences were checked by increasing the number of k points and the energy convergence criteria. In the irreducible part of the Brillouin zone, 12 9 12 9 18 k points were used to calculate the total and partial density of states (PDOS). Quasi-harmonic Debye model implemented in Gibbs package [19, 20] was used to calculate thermo-dynamical behavior of LaMgX (X = Ga, In, Tl). In quasi-harmonic Debye model the non equilibrium Gibbs function G* (V; P, T) was in the form of 

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