The structural, electronic, thermoelectric, magnetic, thermodynamic, elastic, and optical properties of the antiperovskite compound CaCNi \(_3\) are explored from first principles using DFT-based TB-mBJ and GGA \(+U\) methods. Structural optimisation validates system stability at a ground-state energy of \(-10552.36\) Ry and an equilibrium volume of around 378 a.u \(^3\) . The electron localisation function (ELF) shows significant covalent and ionic bonding, whereas electronic structure simulations show a metallic nature dominated by Ni-3d orbitals. The BoltzTraP evaluation of thermoelectric performance indicates moderate energy conversion potential, with a maximum figure of merit of \(ZT \approx 0.26\) at 1000K at \(\mu = +0.035\) eV. Pugh’s ratio = 2.23 confirms mechanical stability and ductility, while decreasing Gibbs free energy and increasing entropy up to 1200 K indicate thermodynamic stability. GGA \(+U\) magnetic analysis shows a limited net magnetic moment in CaCNi \(_3\) , which is confirmed by the spin-polarized density of states (DOS), which shows asymmetric spin channels and validates its ferromagnetic metallic nature. Optical examination confirms metallic behaviour with strong UV absorption ( \(\varepsilon _2\) peak \(\sim 8\) eV), high reflectivity ( \(\sim 0.83\) ), and a large static dielectric constant ( \(\varepsilon _1(0) = 35.50\) ). CaCNi \(_3\) is a versatile material for high-temperature thermoelectrics, spintronics, and optoelectronics.
