Structural, phononic, opto-electronic and elasto-mechanical properties of LiXBe (X = N, P) half Heusler compounds

The plethora of properties associated with half Heusler compounds has made them apposite materials for functional applications significantly in thermoelectrics, solar harvesting, semiconducting and spintronics. The current study invested the exertions in unveiling the details of physical properties of LiXBe (X = N, P) compounds using DFT based VASP and WIEN2k codes considering PBE-GGA and TB-mBJ exchange correlation functionals. Titled compounds successfully assured the stability checks regarding energetic, lattice dynamic and mechanical. By means of electronic structure calculations, TB-mBJ functional disclosed the precise band gaps of 6.912 and 2.340 eV for LiNBe and LiPBe compounds respectively. Fat-band character analysis and partial charge density distributions in HOMO and LUMO orbitals revealed the governess of band edges around Fermi-level by homo-site (N-2p & N-2s) states in LiNBe and hetero-site (P-2p & Li-2s) states in LiPBe compound. The COHP examination and bond order characteristics evidenced comparatively strongest bonding interactions of X-Be than Li-Be bonding pair. The calculated opto-electronic properties; complex dielectric function, optical conductivity, loss function and refractive index have been discussed with substantial details. Physio-mechanical parameters and mechanical anisotropy have been comprehensibly elaborated.