%0 Journal Article
%T Structural and Electronic Properties of Pure Ta, TaNO, and TaZrNO with Ab Initio Calculations
%A T. Chihi
%A M. Fatmi
%A M. Guemmaz
%A J. C. Parlebas
%J ISRN Metallurgy
%D 2012
%R 10.5402/2012/456762
%X This paper presents the results of self-consistent first-principle calculations for the crystal structure and electronic structure of pure tantalum, TaNO, and TaZrNO within density functional theory (DFT) for the sake of comparison and shows the influence of allowing elements on the interatomic distance and the Fermi level. The large total densities of states (TDOS) value for TaZrNO implies the highest electronic conductivity. The difference in values is due to the Zr metallic atoms presence in TaZrNO compound. There is a strong interaction between Ta and (N, O) ( , ) in TaON compound, and Zr presence increases this interaction ( , ) in TaZrON compound. 1. Introduction The elemental tantalum Ta crystallizes in three crystalline phases, bcc-Ta (¦Á-phase), f.c.c-Ta, and a new phase which is now generally referred to as -tantalum. The discoverers of the tetragonal tantalum -Ta (a metastable phase), in 1965 are Read and Altman [1]. It has been attracting much interest in most applications because of its high resistivity (170¨C210£¿ ) [2¨C5]. It is preferred for fabricating capacitors and resistors. The chemical stability and robust mechanical properties of Ta make it a particularly desirable material. Numerous crystal structures have been reported for -Ta. A tetragonal unit cell Ta was proposed by Read and Altman [1] Das [6] proposed a bcc-based superlattice structure, while Burbank [7] proposed a hexagonal hcp structure and -uranium model that was also proposed by Arakcheeva et al. [8, 9] on the basis of X-ray diffraction (XRD) study on single crystals of -Ta produced through electrolytic crystallization, and in the end, the anomalous f.c.c-Ta structure was observed in very thin films of tantalum [10, 11]. On the other hand, nitride formation is common to most transition elements. Many compositional and structural forms exist, with many transition elements forming several different nitride phases. In many of these compounds, nitrogen atoms occupy interstitial lattice sites because they are smaller than the metal atoms. For this reason, they are often referred to as interstitial compounds. Transition metal nitrides are refractory metals that possess technologically useful properties including superconductivity and ultrahigh hardness, and they combine various physical and chemical properties, such as high melting points (around 3000¡ãC). They also possess electronic and magnetic properties that make them useful as electronic and magnetic components and as superconductors [12]. Although monometallic nitrides have been the object of considerable studies [13¨C15],
%U http://www.hindawi.com/journals/isrn.metallurgy/2012/456762/