Elastic Properties of <i>&alpha;</i>- and <i>&beta;</i>-phases of Li₃N

Abstract

Investigations of elastic properties of Li 3 N in both α-and β-phases have been made by firstprinciples methods (HF-LCAO, DFT as implemented in CRYSTAL98 and in CASTEP).The theoretical equation of state of the β-phase (D 4 6h structure) produced by our totalenergy calculations is compared with the experimental EOS. Five independent elastic constants are calculated for the first time for both the phases. These are compared with the available four elastic constants of α-Li 3 N estimated from the slopes of the acoustic branches in the long wavelength region of the measured phonon dispersion curves. The aggregate elastic moduli (B, G, E), the Poisson's ratio ( ) and the Debye temperature Θ D as a function of pressure are also calculated and the results discussed.

Structural Stability, Electronic Structure and Mechanical Properties of Li–N–H System

“…This is in good agreement with the experimental value a 0 = 5.047 Å [20]. The calculated lattice constants are in good agreement with the experimental results [18][19][20][21][22]38] and previous theoretical results [7,14,16,25,27,36,37]. The cohesive energies of these materials are observed to be higher than those of the host elements.…”

“…The Born-Huang elastic stability criteria [45] Tables 3 and 4 along with the available data [9,16,46]. Clearly, the calculated elastic constants for Li 3 N and Li 2 NH under normal and high pressure and LiNH 2 at normal pressure satisfy Born-Huang criteria, suggesting that they are mechanically stable.…”

“…The existence of high pressure b-phase was confirmed by experiments, and their behavior at high pressure was studied [7,[13][14][15]. Hossain et al [16] studied the elastic properties of aand b-phases of Li 3 N by means of first principles calculations. The interaction between LiNH 2 and LiH was investigated by Chen et al [17] and noticed that hydrogen can be reversibly stored in lithium nitride.…”

Elastic properties of mono- and poly-crystalline PbO-type FeSe1−xTex (x=0–1.0): A first-principles study

“…The bulk moduli (B H ), shear moduli (G H ), Young's moduli (Y), and Poisson's ratios (ν) in the Voigt-Reuss-Hill approximation for polycrystalline FeSe 1-x Te x are presented in Table 2. The expression for Reuss and Voigt moduli can be found elsewhere (see [27]). We compare the values with those of polycrystalline elastic moduli of LaFeAsO, LiFeAs and SrFe 2 As 2 [28,29].…”

Superconductivity in Diamond-like BC₃ Phase

“…The expression for Reuss and Voigt moduli can be found elsewhere. 22 The Young's modulus Y and Poisson's ratio ν are then computed from these values using the relationship: Y = 9BG/(3B+G), ν = (3B-Y)/6B. As compared with other superconductors, t-BC 3 is a hard material.…”