Chemical bonding and mechanical properties of M₂AC (M = Ti, V, Cr, A = Al, Si, P, S) ceramics from first-principles investigations

MAX-phase carbides (M is an early transition metal, A is an A-group element) exhibit an interesting bonding characteristic of alternative stacking of strong M–C bonds and relatively weak M–A bonds in one direction. In the present first-principles total energy calculations, we establish the relationship between mechanical properties and electronic structure for ternary M₂AC (M = Ti, V, Cr, A = Al, Si, P, S) carbides. By systematically tuning elements on the M and A sites, pronounced enhancements of bulk modulus, elastic stiffness, and ideal shear strength are achieved in V-containing V₂AC (A = Al, Si, P, and S) carbides. It is suggested that tailoring on the A site is more efficient than on the M site in strengthening the mechanical properties of studied serial carbides. The results highlight a general trend for tailor-made mechanical properties of ternary M₂AC carbides by control of chemical bonding.