Ab initio calculation of the electronic, mechanical, and thermodynamic properties of yttrium nitride with the rocksalt structure

Abstract

The electronic, mechanical, and thermodynamic properties of yttrium nitride with the rocksalt structure have been systematically investigated by using the projector augmented wave method. The calculated results compare very well with available experimental and theoretical results. To properly describe the electronic properties, the generalized gradient approximation GGA(PW91) + U and GGA(PBE) + U theoretical formalisms have been employed. Generally, the PW91 functional provides a slightly more optimal agreement with other theoretical results at lower U energy than PBE does. We calculated the elastic constants of YN based on the GGA and GGA + U methods, and obtained the elastic moduli, brittle/ductile characteristics, Possion's ratio, the hardness, various wave velocities, and Debye temperature of YN. It is shown that Hubbard U correction has a certain impact on the mechanical properties of YN. The heat capacity Cv and the entropy S in the temperature range of 0–2200 K are obtained based on the phonon method and the Debye model. It is revealed that the entropies obtained by the two methods are consistent with the experiment results. The dependencies of the heat capacity Cp, Debye temperature, the Grüneisen parameter, and the thermal expansion coefficient on pressure and temperature are also obtained in the ranges of 0–120 GPa and 0–2200 K by using the Debye model.

An Ab Initio Study of Pressure-Induced Reversal of Elastically Stiff and Soft Directions in YN and ScN and Its Effect in Nanocomposites Containing These Nitrides

“…Next, we have also checked the electronic properties of both materials which are predicted to be semiconductors in their ground state. This is in agreement with previous studies [19,20,23] but our value of the band-gap energy width (0.34 eV) is underestimated similarly as in previous theoretical studies in which similar computational methods were used—see a detailed discussion in Reference [20]. The pressure-dependences of the width of the energy band-gap in their electronic structures are depicted in Figure 5b.…”

“…As far as the ground-state properties of B1-structure YN and ScN are concerned, the calculated equilibrium lattice parameters are in an excellent agreement with those previously obtained that employed different variants of the GGA exchange-correlation approximations as well as with experimental results. In particular, we find the lattice parameter of YN to be 4.916 Å when theoretical values 4.90–4.93 Å were reported in Reference [19], 4.619 Å in [20], 4.93 Å in [21,36], 4.85 Å in [23] and the experimental value is 4.88 Å [37]. Regarding ScN, our value 4.510 Å agrees with theoretical ones of 4.543 Å from [24], 4.516 Å reported in Reference [38], 4.50 Å in [23] and experimental 4.50 Å [39].…”

“…The authors of that study also applied the Hubbard on-site correlation U term (GGA+U) and reported improvement in the accuracy of the calculation of the bandgap and selected features of the electronic structure of YN which are relevant to transport properties, such as transverse and longitudinal conduction band effective mass. The GGA+U calculations were also performed in the study of electronic, mechanical, and thermodynamic properties of YN in [20]. Other theoretical studies were focused on the stability of the rock-salt B1 structure of YN with respect to a pressure-induced transition into another phase, such as the caesium-chloride B2 one [21,22].…”

The role of the Scandium element concentration in the YN matrix: Ab initio study of structural, electronic, mechanical and thermal properties

“…For the binaries, the hardness values H v1 (H v2 ) for ScN is higher by 6.18% (5.98%) compared with YN material, this is due to the fact that ScN has a shorter bond length, a lower bond ionicity and a lower mass density compared to YN. Hardness parameters of YN are close to theoretical values [11], which give values 21.009 GPa (21.837GPa), while in ScN, it is slightly larger than the value of 24.9 GPa reported by Liu et al [41]. For ternaries, the hardness showed in the Figure 7, increases with Scandium concentration.…”

“…The shear modulus G is defined as arithmetic average of the G V (Voigt's shear modulus) [37] and G R (Reuss's shear modulus) [38], which are the upper and lower respectively estimates values of the shear modulus. The definition of bulk modulus B is in the same way as defined the shear modulus G. The Young's modulus (Y) and the Poisson's ratio (ν) are obtained from the bulk and shear modulus and are expressed as [38]: [11] using FPLAPW+GGA, d Reference [11] using FPLAPW+GGA, g Reference [52] using VASP+GGA, h Reference [51] using PP-PW + GGA.…”