Materials Sciences and Applications, 2011, 2, 1383-1391 doi:10.4236/msa.2011.210187 Published Online October 2011 (http://www.SciRP.org/journal/msa) Copyright © 2011 SciRes. MSA 1383 Structure and Bonding of Nanolayered Ternary Phosphides Abdelkader Yakoubi 1* , Hanane Mebtouche 1 , Mohamed Ameri 2 , Bachir Bouhafs 1 1 Modeling and Simulation in Materials Science Laboratory, Physics Department, University of Sidi Bel-Abbes, Sidi Bel-Abbes, Al- geria; 2 Département de Physique, Faculté des Sciences, Université Djillali Liabès, Sidi-Bel-Abbès, Algeria. Email: * yakoubi_aek@yahoo.fr Received April 2 nd , 2011; revised April 25 th , 2011; accepted May 25 th , 2011. ABSTRACT We have studied the electronic structure and chemical bonding mechanism of nanolayered M 2 SbP with M = Ti, Zr and Hf using the full-relativistic of an all-electron full potential linearized augmented-plane-wave (FP-LAPW) method based on the density functional theory, within the local density approximation scheme for the exchange-correlation potential. Furthermore, we have to calculate the energy of formation for prove the existence of these compounds experimentally. Geometrical optimizations of the unit cell are in good agreement with the available theoretical and experimental data. The bulk modulus of M 2 SbP conserved as Ti is replaced with Zr, and increases by 8.7% as Ti is replaced with Hf, which can be understood on the basis of the increased number of valence electrons filling the p-d hybridized bonding states. The bonding is of covalent-ionic nature with the presence of metallic character. Analyzing the bonding in the binary MP, it can be concluded that this character is essentially conserved in M 2 SbP ternaries. Keywords: Ceramics, Ab-Initio Calculations, Electronic Structure, Crystal Structure, Equations-of-State 1. Introduction M n+1 AX n (MAX) (n = 1 to 3) phases are a series of ce- ramics but with a combination of ductility, conductivity and machinability comparable to metals. M is an early transition metal, A is an A-group element (mostly IIIA and IVA) and X is either C or N. These phases have hexagonal layered structures and belong to the space group P6 3 /mmc, where in M n+1 X n layers interleaved with pure layers of the A-group elements. The structures of the vast majority of these compounds were determined by Nowotny [1] and co-workers in the sixties. The MAX phases are typical representatives of nano- laminated phases, and according to M. W. Barsoum et al. [2,3], these phase characterized by high elastic moduli, are machinable [4], exhibit good damage tolerance [5], excellent thermal shock resistance [6], and good corro- sion resistance [7], and they are good thermal and elec- trical conductors [4]. This unique combination of proper- ties serves as motivation for fundamental as well as ap- plied research. MAX phases are used as formers for healthcare products, hot pressing tools, and resistance heating elements [8,9], and are suitable for many tech- nological applications. Extensive experimental and theoretical studies were reported on MAX phases because of their special me- chanical, thermal and electrical properties. A. D. Bor- tolozo et al. [10] investigated Ti 2 InC by x-ray diffraction, magnetic and resistivity measurements. This work sus- tains the idea of the existence of a new class of super- conducting materials that crystallizes in the Cr 2 AlC pro- totype. T. Scabarozi et al. [11] report on correlations between thermal expansion, elastic modulii, thermal transport, specific heat, and electrical transport measurements of materials within the MAX-phase family. Elastic modulus measurements are made using an ultrasonic time of flight technique. Thermal expansion measurements are made using high-temperature x-ray diffractions. Also, the electronic properties of these materials have been studied both theoretically and experimentally [12]. For MAX-phases in thin film form, the processing and physical properties have been recently reviewed.[13] Because the MAX-phases crystallize in a hexagonal struc- ture the anisotropy of its conductivity is of great interest but it has been difficult to experimentally resolve this issue [14,15]. This design criteria is not only limited to the carbides