G. Surucu

First-Principles Study on the MAX Phases Ti n+1GaN n (n = 1,2, and 3)

We have performed first-principles density functional theory calculations within generalized-gradient approximation to obtain the structural, mechanical, electronic, and dynamic properties of Tin+1GaNn compounds. In order to examine the stability of these compounds, formation enthalpies, single-crystal elastic constants, and phonon dispersion curves were calculated. We show that all compounds are stable, while α-Ti4GaN3 is the most stable. The density of states calculations also demonstrate that all of the compounds are metallic. Additionally, bonding nature and related characteristics such as Mulliken atomic charges and bond overlap populations were investigated. Furthermore, thermodynamic properties were calculated by means of phonon dispersion curves. The results are compared in this work with available experimental values and theoretical calculations.

First-principles study of structural, elastic, lattice dynamical and thermodynamical properties of GdX (X = Bi, Sb)

The results are presented of first-principles calculations of the structural, elastic and lattice dynamical properties of GdX (X = Bi, Sb). In particular, the lattice parameters, bulk modulus, phonon dispersion curves, elastic constants and their related quantities, such as Youngs modulus, Shear modulus, Zener anisotropy factor, Poissons ratio, Kleinman parameter, and longitudinal, transverse and average sound velocities, were calculated and compared with available experimental and other theoretical data. The temperature and pressure variations of the volume, bulk modulus, thermal expansion coefficient, heat capacities, Grüneisen parameter and Debye temperatures were predicted in wide pressure (0−50 GPa) and temperature ranges (0–500 K). The plane-wave pseudopotential approach to the density-functional theory within the GGA approximation implemented in VASP (Vienna ab initio simulation package) was used in all computations.

Ab-initio studies of some rare-earth borides: CeB2, PrB2, NdB2, and PmB2

Abstract The structural, mechanical and thermal properties of CeB2, PrB2, NdB2, and PmB2 compounds in hexagonal AlB2-type (P6/mmm) and ReB2-type structures (P63/mmc) are investigated using density functional theory. The results indicate that those compounds with hexagonal AlB2 structure are the most stable among the considered structures. The mechanical properties are calculated according to the elastic constants by means of the Voigt–Reuss–Hill averaging scheme. The temperature dependence of various quantities such bulk modulus, Debye temperature, thermal expansion, heat capacity, and Grüneisen parameter have been analyzed using the quasi-harmonic Debye model.