We have studied the physical properties of M 2 InC (M = Zr, Hf and Ta) MAX phases ternary carbides using density functional theory (DFT) methodology. The structural, elastic and electronic properties are revisited (and found to be in good agreement with recently reported results). The charge density distribution, Fermi surface features, Vickers hardness, dynamical stability, thermodynamics and optical properties have been investigated for the first time. The calculated single crystal elastic constants and phonon dispersion curves endorse the mechanical and dynamical stability of all the compounds under study. The calculated single crystal elastic constants C ij and polycrystalline elastic constants are found to increase with increasing atomic number of M species (M = Zr, Hf and Ta). The values of Pugh ratio and Poisson"s ratio revealed the brittleness of the compounds under study associated with strong directional covalent bond with a mixture of ionic contribution. Overlapping of conduction band and valence band at Fermi level notify the metallic nature of M 2 InC (M = Zr, Hf and Ta) MAX phases. Low values of Vicker hardness indicate the softness of the materials and easy machinability.. The thermodynamic properties, such as the free energy, enthalpy, entropy, specific heat capacity and Debye temperature are evaluated using the phonon dispersion curves and a good correspondence is found with the M atomic species. Electronically important optical properties, e.g., dielectric functions, refractive index, photoconductivity, absorption coefficient, loss function and reflectivity are calculated and discussed in detail in this study. The term "M n+1 AX n phases" was coined by Barsoum in 2000 for the first time [1]. In the general formula M n+1 AX n with n = 1-3, M = early transition metal; A= which? group element and X= C and/or N). The MAX phases M 2 AX, M 3 AX 2 and M 4 AX 3 are referred as 211, 312, and 413 subject to the value of n. The M n+1 AX n phases are crystallized in the hexagonal structure belonging to the space group of P6 3 /mmc. The MAX phase nano layered ternary compounds are suitable for many technological applications owing to an unique combination of both metallic and ceramic properties. Like metals, they exhibit good electrical and thermal conductivity, machinability, low hardness, thermal shock resistance, and damage tolerance.On the other hand, these compounds possess ceramiclike high elastic moduli, high melting temperature, and oxidation and corrosion resistance [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. There are forty eight 211 phases that have already been listed without considering possible solid solutions, however more have been theoretically predicted [1,[18][19][20][21][22]. Furthermore, very recently the MAX phase materials are used as a precursor to synthesize atomically thin two-dimensional materials with many attractive physical features, the so called MXenes [23].The extensive research effort has been paid on both theoretical and experimental study of M 2 AX phases [2]...

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