Abstract
We have performed ab initio calculations for the nanolaminates Zr(2)AC (A = Ti, In, Tl, Si, Ge, Sn, Pb, P. As, S) ceramics to study their electronic structure, elastic and optical properties. In this work, we used the accurate augmented plane wave plus local orbital method with density functional theory to find the equilibrium structural parameters, dielectric functions and to compute the full elastic tensors. The obtained elastic constants were used to quantify the stiffness of the Zr(2)AC phases and to appraise their mechanical stability. The relationship between elastic, electronic and valence electron concentration is discussed. Our results show that the bulk modulus and shear modulus increase across the periodic table for Zr(2)AC. Furthermore, trends in elastic stiffness are well explained in terms of electronic structure analysis, as occupation of valence electrons in states near the Fermi level of Zr(2)AC. We show that increments of bulk moduli originate from additional valence electrons filling states involving Zr d-A p. We show also that Zr d-A p hybridizations are located just below the Fermi level and are weaker bonds than the Zr d-C p hybridizations, which are deeper in energy. As a function of the p-state filling of the A element the Zr d-A p bands are driven to deeper energy. The optical spectra were analyzed by means of the electronic structure, which provides theoretical understanding of the conduction mechanism of these ceramics. (C) 2010 Elsevier Masson SAS. All rights reserved.