Structures and Properties of β-Titanium Alloys Doped with Trace Transition Metals: A Density Functional Theory Study

We systematically calculate the structure, formation enthalpy, formation free energy, elastic constants and electronic structure of Ti 0.98 X 0.02 system by density functional theory (DFT) simulations to explore the effect of transition metal X (X = Ag, Cd, Co, Cr, Cu, Fe, Mn, Mo, Nb, Ni, Pd, Rh, Ru, Tc, and Zn) on the stability mechanism of β-titanium. Based on our calculations, the results of formation enthalpy and free energy show that the adding small amounts of X is beneficial to the thermodynamic stability of β-titanium. This behavior is well explained by the density of state (DOS). However, the tetragonal shear moduli of Ti 0.98 X 0.02 systems are negative, indicating that β-titanium doping with a low concentration of X is still elastically unstable at 0 K. Therefore, we theoretically explain that β-titanium doped with trace transition metal X is unstable in the ground state.