Ab initio study of structural, electronic, elastic, and phonon properties of ScN and ScP at ambient and high pressure

The structural, electronic, and elastic properties of ScN and ScP in NaCl (B-1 phase) and CsCl (B-2 phase) structures and the phonon dispersion at ambient and high pressure, close to phase transition, have been investigated by using first-principles pseudopotential method in the framework of density functional theory with the generalized gradient approximation. It is found that both compounds are stable in B-1 phase at ambient pressure and undergo a structural phase transition to B-2 phase at 368.76 and 247.56GPa, respectively. ScN is a semiconductor and ScP is semimetallic at ambient pressure (B-1 phase), whereas both the compounds are metallic at high pressure (B-2 phase). The calculated lattice parameter (a), bulk modulus (B), and their first-order pressure derivative (B') are in good agreement with previous calculations. The elastic constants (C-11, C-12, and C-44) have been calculated in both phases. We also report the phonon structure of these compounds at ambient and close to the phase-transition pressure and compared among themselves. It is shown that their phonon structures are consistent with electronic properties at ambient and high pressures. Near B-1-B-2 transition, the LA mode at X-point softens considerably leading to structural instability. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim