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

Abstract

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 247.56 GPa, 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 0 ) 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.

Trends in the elastic response of binary early transition metal nitrides

“…A comparison with previous DFT-GGA literature data 21,22,40,41,43,44,49 yields, apart from a few exceptions, a good agreement with our results. The local density approximation (LDA) based C 11 elastic constants from the literature 20,42,47 are higher than our GGA-based data. This is a consequence of over-and under-binding of LDA and GGA, respectively, resulting in too small lattice constants and consequently too hard elastic constants in LDA.…”

FP-LAPW investigation of mechanical and thermodynamic properties of Na2X (X = S and Se) under pressure and temperature effects

“…At low temperatures, the shapes of the curves of C V and C P are similar. As known, the increase of heat capacity with T 3 at low temperatures is due to the harmonic approximation of the [29], c [26], d [20], e [62], f [63], g [64], h [65], i [66], k [67], l [23], m [68], n [69], o [31], p [70]. Debye model.…”

“…We further studied the high-pressure elastic behavior of Na 2 S and Na 2 Se by computing the second-order elastic constants and their variation [28], f [63], m [68], o [31].…”

Electronic, structural, and elastic properties of metal nitrides XN (X = Sc, Y): A first principle study

“…There has been great interest in transition-metal nitrides in the past several decades [1][2][3][4]. This interest is fueled by their many potential, technological applications, including high hardness, [5] high temperature stability [6], mechanical strength [7][8][9], magnetic [10], and electronic properties that vary from semiconducting to metallic phases [11][12][13][14][15][16][17][18][19][20][21][22]. These unique properties make XN useful refractory materials and hard coatings for cutting tools [11][12][13] .…”

“…The aforementioned properties of these materials motivated a variety of experimental [6-8, 11, 12, 14, 15, 22-27] as well as theoretical studies [3,9,9,10,13,[16][17][18][19][20][21][28][29][30][31][32][33][34][35] with the latter utilizing computational techniques of varying sophistication, ranging from the tight binding and the empirical pseudopotential methods to ab-initio density functional theory (DFT).…”