First-principles Study of Structural, Electronic, Elastic, Phonon, and Thermodynamical Properties of the Niobium Carbide Nikita Rathod 1,2,a , S.D. Gupta 2,b , S.K. Gupta 2,c and Prafulla K. Jha 2,d 1 Department of Physics, Bhavnagar University, Bhavnagar-364022, India 2 Vadodara Institute of Engineering, Vadodara- 391510, India a rathod.nikita13@gmail.com, b guptasanjay.56@gmail.com, c skgupta.physics@gmail.com, d prafullaj@yahoo.com Key words: Carbide, Density Functional Theory, Phonon, Thermal Properties Abstract. A detailed theoretical study of structural, electronic and vibrational properties of niobium carbide are carried out in rocksalt phase using the density functional theory implemented in ABINIT code. The calculated structural parameters like lattice constant and bulk modulus agree well with the available data. The Zener anisotropy factor (A), Poison's ratio (v), Young’s modulus (Y) and shear modulus (C’) are also presented. The electronic band structure and density of states are presented and discussed in light of bonding nature in NbC. The band structure indicates its metallic nature. The calculated phonon dispersion curves show that the NbC in rocksalt phase has all positive phonons throughout the Brillouin zone. The thermodynamical properties are also presented and discussed. 1. Introduction Transition metal mono carbides and nitrides are scientifically interesting and promising materials for various industrial applications such as suitable metal gates in the new generation of complementary metal oxide semiconductor technology [1]. Presently scientific interest is to develop within the microelectronic industry for the use of transition metal mono carbides and nitrides especially niobium carbide (NbC) and niobium nitride (NbN) as an electrical conductivity barrier due to its high superconducting temperature (T c ≈ 20K) [2]. The specific combination of thermal, electrical and mechanical properties such as high melting temperature, high hardness, high-temperature strength, good electrical and thermal conductivity of transition metal mono carbides posses a special attention. These properties are the expression of the interaction of the three different type of bonding; metallic, ionic and covalent which gives unusual combinations of bonding mechanism and manifests itself in their macroscopical properties. The over all bonding nature of mono carbides can be described as covalent of N and metal states, but there is also some ionic character with electron transfer from the metal to nitrogen atoms. In addition the metallic character is responsible for making transition metal carbides ultra hard [3-8]. These mono carbides are also used as high-temperature structural materials in the form of hard constituents in metal matrix composites [9–10], in adsorption, in catalytic properties and in surface chemical reactivity [11]. These properties of transition metal carbides have lead to technological applications in developing wear-resistant coatings for ball bearings and cutting machine tools [1]. Most of the unusual features of transition metal carbides (TMCs) in particular depends on occupancy of number of d-electrons and to reveal these properties, several first principles calculations have been conducted in the recent and past with regards to the bulk properties of these materials particularly for the properties categorizing for niobium carbide among refractory materials, which are usually associated with typical covalent character [13]. The rigorous understanding of the Solid State Phenomena Vol. 171 (2011) pp 67-77 Online available since 2011/May/17 at www.scientific.net © (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/SSP.171.67 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 117.211.84.58-03/06/11,12:55:19)