Structural, elastic and mechanical properties of Ti–15Nb–xGe alloys: insight from DFT calculations

We theoretically investigated the structural, elastic and mechanical properties of Ti–15Nb–xGe alloys with x = 0.8, 1, 1.2, 1.4, 1.6 and 1.8 (wt%) compositions for the first time. Theoretical calculations were performed with the generalized gradient approximation (GGA) functional within density functional theory (DFT). We employed the Perdew–Burke–Ernzerhof (PBE) scheme and the virtual crystal approximation (VCA) in this study. We determined the elastic constants, bulk, shear and Young’s moduli, Pugh ratio, Poisson’s ratio, universal anisotropy and hardness of all the alloys under varying Ge% concentrations. All studied compositions of the alloys show structural stability. Young’s moduli values were obtained as 43 and 14.8 GPa for Ti–15Nb–0.8Ge and Ti–15Nb–1.8Ge alloys, respectively, which compare well to the Young’s moduli range of human cortical bone with 10–30 GPa. Except the Poisson’s and Pugh ratios, all other computed parameters of the alloys were found to decrease under increasing Ge concentrations. Further, all investigated alloys exhibit desired ductile mechanical behaviour of biomaterials and calculated hardness values of these alloys are satisfactory with the hardness of human teeth dentin.