Lattice dynamics of boron phosphide

Abstract

Using the density-functional theory, normconserving pseudopotenlials and plane-wave expansion$ we have calculated ab initio the equation of state and the principal phonon modes in boron phosphide, including their pressure dependence and the amplitude of the eigendisplacemenls. Good agreement with experiment is obtained, whenever a comparison is possible: in fact, most of the results are predictions. A tenparameter valence overlap Shell model is then mnslrucled from the available experimental dala, which are completed by the data obtained in the first-principle calculations: fm7snphonon ffequencies and eigenvectors The previous speculations about the anomalous behaviour of the effeclive charges are discussed in the conte~t of the present re5ults.

Phonons and their pressure dependence of MnAs and MnN by ab initio calculations

“…It is interesting to remark that zb-MnAs show flatter TO bands over the entire Brillouin zone. Moreover, it has been verified from the obtained results that there is no soft mode at the W-point of the Brillouin zone (the W 1 mode), as observed in the previous LDA calculations [7] with the following feature: instead of having negative values of its Grüneisen parameter [12], have negative frequency value, as observed for cubic HfO 2 and ZrO 2 [13]. This is a clear indication that the "overbinding effect" [9] verified in LDA calculations causes an elastic instability of the zb-MnAs, with the above characteristics, which is not observed in the GGA ones.…”

Boron phosphide as the buffer-layer for the epitaxial III-nitride growth: A theoretical study

“…With this model, we have successfully described the (2 Â 1) reconstruction pattern of both SiC [11] and GaAs [12] (1 0 0) surfaces, as well as the N adsorption over the GaAs (1 0 0) surfaces [12]. For the slab lattice parameters, we have used our calculated equilibrium bulk lattice parameter for cubic BP, 4.48 Å , obtained with a cutoff energy of 60 H (120 Ry) for the plane waves and 10 special k-points, which are in good agreement with previous calculations, as well as with the experimental data [13][14][15][16][17]. Also, in the slab calculations, a (4 4 2) Monkhorst-Pack set of k-points was used to sample the slab Brillouin zone [18], and we kept the same cutoff energy for the plane-waves used in the bulk calculations.…”

Lattice dynamical theory of thermal expansion and mode Grüneisen parameters in cubic BP

“…In spite of numerous experimental efforts, the amount of theoretical understanding for the electronic properties has been limited to a handful of studies [13][14][15][16][17][18] and, in particular, the knowledge of the vibrational and thermal properties of BP are rather scarce. 19 By using the norm-conserving pseudopotentials and plane wave expansions within density functional theory, Alves and Kunc 19 reported calculations for the phonon frequencies and Grüneisen parameters ␥'s at critical points in BP. To the best of our knowledge, there exists no theoretical study in BP that deals with the variation of the thermal expansion coefficient ␣(T) or Grüneisen parameter ␥(T) with temperature.…”