Journal of Modern Physics, 2012, 3, 1891-1894

http://dx.doi.org/10.4236/jmp.2012.312238 Published Online December 2012 (http://www.SciRP.org/journal/jmp)

Ab-Initio Structural Study of SrMoO3 Perovskite

Avinash Daga, Smita Sharma

Government Dungar College, Bikaner, India

Email: avinashdaga2009@gmail.com, smita_sharma_bkn@yahoo.com

Received August 10, 2012; revised September 27, 2012; accepted October 10, 2012

ABSTRACT

The equilibrium crystal structure parameter and bulk modulus of the SrMoO3 perovskite has been calculated with

ab-initio method based on density functional theory (DFT) using both local density approximation (LDA) and general-

ized gradient approximation (GGA). The corresponding total free energy along with its various components for SrMoO3

was obtained. The lattice parameter and bulk modulus calculated for SrMoO3 within LDA are 3.99 Å and 143.025 GPa

respectively whereas within GGA are 4.04 Å and 146.14 GPa respectively, both agree well with the available experi-

mental data. The total energy calculated within LDA and GGA is almost the same however lower results are obtained

for GGA. All calculations have been carried out using ABINIT computer code.

Keywords: Perovskite; DFT; LDA; GGA; ABINIT

1. Introduction

Crystal and electronic structures of solid materials are

crucial to understand and improve properties. Many

technological applications, including catalysis, micro-

electronics, substrates for growth of high Tc supercon-

ductors, etc., are based on thin films of ABO3 perovskite.

Until recently, 4d transition metal oxides (TMO) have

attracted less attention because they had the crystalline

defects and having more extended d-orbitals compared to

3d TMO. Yet, numerous studies have shown that this is

no longer the case for some promising TMO such as

molybdates. These oxides are observed to exhibit un-

conventional superconductivity [1] and research is going

on to understand the mechanism [2] of this new quantum

order due to strong electron-electron interaction. Pseudo

gap formation [3], metal-insulator transitions [4,5] and

high-voltage applications are the other significant prop-

erties which draw a considerable attention to 4d TMO.

Some related data were reported by daga et al. [6].

The density functional theory (DFT) is a good ap-

proach for the description of ground state properties of

metals, semiconductors, and insulators. The success of

this technique is that it has allowed us to better under-

stand materials and processes. It has deepened the inter-

pretation of experimental findings. We have used AB-

INIT computer code in order to perform first-principles

DFT calculations. This code is open source ab initio elec-

tronic structure calculation software and has been under

continuous development.

In the present study we calculated lattice constant,

bulk modulus and total energy along with its components

for SrMoO3 perovskite. The chosen perovskite has sim-

ple, cubic Pm3m symmetry.

2. Calculation Method

There are some approximations existing which permit the

calculation of certain physical quantities quite accurately.

In physics the most widely used and the simplest ap-

proximation is the local-density approximation (LDA). It

is based upon exact exchange energy for a uniform elec-

tron gas. The unknown part is exchange-correlation part

of the total-energy functional and it must be approxi-

mated. The functional depends only on the density at the

coordinate. Generalized gradient approximations (GGA)

are still local but also take into account the gradient of

the density at the same coordinate.

In this work, LDA and GGA density functionals are

considered for computation of lattice parameter, bulk

modulus and the total energy. The calculations are carried

out using numerical implementation of the formulation of

DFT; the ABINIT code, based on the DFT using plane

waves and pseudopotentials. Plane waves are used as a

basis set for the electronic wave functions. Many input

variables are needed to run the ABINIT code for the cal-

culations. The main input variables have been listed in

Table 1. “Spgroup” defines space group number of the

perovskite in the input file. “acell” parameter gives the

length scales by which dimensionless primitive transla-

tions are to be multiplied and is specified in Bohr atomic

units. We include input variables “ntypat” and “znucl”,

where “ntypat” gives the number of types of atoms and

“znucl” gives nuclear charge Z of the elements in order

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