High-pressure studies on the properties of FeGa3: Role of on-site Coulomb correlation

High-pressure x-ray diffraction measurements have been carried out on the intermetallic semiconductor FeGa3 and the equation of state for FeGa3 has been determined. First-principles based DFT calculations within the GGA approximation indicate that although the unit cell volume matches well with the experimentally obtained value at ambient pressure, it is significantly underestimated at high pressures and the difference between them increases as pressure increases. GGA + U calculations with increasing values of U-Fe(3d) (on-site Coulomb repulsion between the Fe 3d electrons) at high pressures, correct this discrepancy. Further, the GGA + U calculations also show that along with U-Fe(3d), the Fe 3d bandwidth also increases with pressure and around a pressure of 4 GPa, a small density of states appear at the Fermi level. High-pressure resistance measurements carried out on FeGa3 also clearly show a signature of an electronic transition. Beyond the pressure of 19.7 GPa, the diffraction peaks reduce in intensity and are not observable beyond similar to 26 GPa, leading to an amorphous state.