Theoretical study of mechanical, electronic, chemical bonding and optical properties of Ti2SnC, Zr2SnC, Hf2SnC and Nb2SnC

In this work, we investigate structural parameters, elastic stiffness, electronic, bonding and optical properties of four 211 MAX phases compounds, Ti2SnC, Zr2SnC, Hf2SnC and Nb2SnC. These systems exhibit nanolaminated structure where MC layers are interleaved with Sn. We employ first-principles calculations based on density functional theory (DFT) by means of two methods, the full-potential linearized augmented plane-wave and plane-wave pseudopotential. Geometrical optimization of the unit cell is found in good agreement with the available experimental data. Electronic and bonding properties are studied throughout the calculation of densities of states, Fermi surfaces and charge densities. Furthermore, the optical properties are investigated via the calculation of the dielectric tensor component in order to characterize the linear optical properties. The optical spectra are analyzed by means of the electronic structure, which provides theoretical understanding of the conduction mechanism of these ceramics. We gave more attention to the elastic constants, where we have derived bulk and shear modulus using Voigt-Reuss-Hill approach. Elastic parameters and mechanical properties are analyzed from anisotropy and ductility calculations. The Debye temperature is derived using Debye-Gruneisen model. (C) 2009 Elsevier B.V. All rights reserved.