Phonon instability and charge density wave in U₂Ti

Phonon dispersion, structural distortion and the elastic properties of U₂Ti are studied using ab-initio techniques. Our calculations revealed an instability in the hexagonal structure of U₂Ti which is not observed in the earlier studies on this system. This instability is demonstrated through the imaginary phonon frequencies found around the A-point in the Brillouin zone. This instability leads to a Peierl's type of dimerization of U atoms along Z direction which will result in the formation of charge density wave (CDW) in the system. The dimerization leads to a new ground state structure in the system whose unit cell evolve by the doubling of the original cell along the Z direction. Our calculations further showed that the CDW exist in the system up to a pressure of 4 GPa. - Highlights: • An instability is found in the phonon dispersion of U₂Ti. • The instability leads to the Peierl's transition type of dimerization. • Possibility of existence of Charge Density Wave is predicted. • Pressure to suppress this transition is found to be 4 Gpa.