Pressure study of structural properties and phonons in YBa2Cu3O7

The pressure dependence of crystal structure and vibrational properties of YBa2Cu3O7 is investigated by first-principles calculations based on density functional theory. They have determined the optimized geometry for different unit cell volumes by relaxing the atoms to their force-free positions. The tendency of altered bond strength with pressure is consistent with experimental investigations and previous c-axis strain calculations. The pressure effect on the three A1g phonon frequencies dominated by oxygen vibrations is in very good agreement with experimental investigations showing constant linear pressure coefficients dω/dp over a wide range of pressure values