LAUSR

The structural stability of indium was investigated under high pressures up to 247 GPa using synchrotron X-ray diffraction techniques. A reentrant structural transition from a face-centered tetragonal (fct-I with c/a > 1) to a face-centered orthorhombic (fco) and further to an fct-I structure was revealed. The first transition (from fct-I to fco) and the second transition (from fco to fct-I) were observed at approximately 50 GPa and 150 GPa, respectively. The second transition was of the second order despite the first transition being of the first order. The theoretically predicted fct-II (c/a   1) to a face-centered orthorhombic (fco) and further to an fct-I structure was revealed. The first transition (from fct-I to fco) and the second transition (from fco to fct-I) were observed at approximately 50 GPa and 150 GPa, respectively. The second transition was of the second order despite the first transition being of the first order. The theoretically predicted fct-II (c/a < 1) phase was not observed at pressures up to 247 GPa. The equation of state of indium is discussed compared to that of other period 5 elements.