First-principles investigations of elastic stability and electronic structure of cubic platinum carbide under pressure

Abstract

The authors have presented a detailed investigation on the phase stabilities and electronic properties of ideal stoichiometric platinum carbide (PtC) in the rock-salt (RS) and zinc-blende (ZB) structures under high pressure. Theoretical calculations are performed using the first-principles pseudopotential density functional method, in which we employ the generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof form and local density approximation (LDA) of Ceperly and Adler parameterized by Perdew and Zunger together with plane-wave basis sets for expanding the periodic electron density. Through a series of tests, such as the total energy as a function of volume, the Gibbs free energy as a function of pressure, the P-V equation of states, the elastic stabilities, and the electronic band structures of PtC with ZB and RS phases, we have confirmed that the recently synthesized compound PtC is crystallized in the ZB structure at zero pressure and that the RS structure is a high-pressure phase; the phase transition studied from the usual condition of equal enthalpies occurs at the pressures of 46.6 and 46.5 GPa for GGA and LDA calculations, respectively. Our conclusions are consistent with the theoretical prediction obtained from the full-potential linearized augmented plane-wave method, but are reversed with the DAC experimental results and other pseudopotential plane-wave theoretical results. Therefore, the experimental observation of the RS structure in PtC remains a puzzle, and our study indicates that further experimental and theoretical investigations need to be carried out to find the cause of the stability of the PtC.

Debye temperature, thermal expansion, and heat capacity of TcC up to 100GPa

“…Through the analysis of energy-volume variation, we find that the TcC in the NaCl structure is the ground-state phase, and it is contrary to the research results of Sun et al [6][7][8] who reported that the ZnS structure is more stable phase and the NaCl structure is a high-pressure phase for PtC. In fact, most of the transition-metal monocarbides usually crystallize in the cubic NaCl structure [16].…”

“…Their accurate first-principle calculations indicate that the recently synthesized compound PtC is crystallized in the ZnS structure at zero pressure and that the NaCl structure is a high-pressure phase, which the phase transition studied from the usual condition of equal enthalpies occurs at the pressures of 46.6 and 46.5 GPa for GGA and LDA calculations, respectively. In spite of this, the whole set of elastic constants calculated for not only ZnS-but also NaCl-PtC [6][7][8] is all fulfilled the stability criteria for the cubic crystal: ,c 11 > 0, c 44 > 0, and c 11 þ 2c 12 > 0 [9]. From this sense, the synthesized PtC in Ref.…”

“…A very recent paper by Sun et al [6] had given a good work to clarify this open issue from different aspects: the total energy as a function of volume, the Gibbs free energy as a function of pressure, the P-V equation of states, and the electronic band structures. Their accurate first-principle calculations indicate that the recently synthesized compound PtC is crystallized in the ZnS structure at zero pressure and that the NaCl structure is a high-pressure phase, which the phase transition studied from the usual condition of equal enthalpies occurs at the pressures of 46.6 and 46.5 GPa for GGA and LDA calculations, respectively.…”

Электронная структура, механическая и динамическая стабильность гексагональных субкарбидов M-=SUB=-2-=/SUB=-C (M = Tc, Ru, Rh, Pd, Re, Os, Ir, Pt): ab initio расчеты

“…С теоретической точки зрения, в последнее время было проведено боль-шое количество расчетов для предсказания структурных, когезионных, электронных, механических и т. д. свойств этих материалов [2]. Следует отметить, что большинство этих работ посвящено стехиометрическим (C/M = 1) монокарбидам MC, для которых обсуждалась сравни-тельная стабильность их различных гипотетических по-лиморфов, см., например, [2,[11][12][13][14][15][16][17][18][19][20].…”

Structural Stabilities and Elastic Constants of EuX (X = O, S, Se, and Te) Compounds at High Pressure

“…Elastic constant may be the most important mechanical quantity in that the elastic constants of a solid relate to various fundamental solid state properties such as interatomic potentials, equation of state, phonon spectra [30]. Most importantly, knowledge of elastic stiness coecients is essential for many practical applications related to the mechanical properties of a solid.…”