Effect of pressure on structural, electronic and bonding properties of CaTM2Pn2 (TM = Ni, Pd; Pn = P, As) compounds: A full potential computational study

Highlights: ► We have predicted the interlayer bond distance in the compounds namely CaNi2(P/As)2 and CaPd2(P/As)2 as below or around 4.66 a.u. ► There may be changes in the Fermi surface topology of these compounds between 30 GPa - 56 GPa. ► The bond formation between Pn-Pn atoms and/or that between TM-Pn atoms is fluctuating under pressure. ► Under compression, metallization and conductivity of these compounds are enhanced. -- Abstract: The structural, electronic and bonding properties of ThCr2Si2-type compounds, namely, CaTM2Pn2 (TM = Ni, Pd; Pn = P, As) with space group I4/mmm (139) are obtained under compression by means of Full Potential – Linearized Augmented Plane Wave (FP – LAPW) method as implemented in WIEN2K code. The optimized lattice parameter, the positional z-parameter, Fermi energy, Density of States (DOSs) at Fermi Level, electronic specific heat coefficient and the distance between Ni(Pd)–P(As) and P(As)–P(As) atoms at equilibrium lattice configuration and under compressions are reported. Electron density plots, band structure plots and DOS are illustrated and compared. Different bonding characteristics are noted and compared. Our work predicts the possible range of bond lengths for the occurrence of covalent bonding between the pnictogens in these compounds. High pressure band structure calculations reveal the possibility of Electronic Topological Transition (ETT) in these compounds