Unusual flash cooling-induced phase in a crystal of triphenylsilanol

The unique phase in a crystal of triphenylsilanol (Ph₃SiOH) is reported. It is observed that after the crystal is flash-cooled from room temperature to 100 K, a new stable ordered phase II occurs with an increase in the unit-cell parameters compared to the earlier reported phase I. The new phase II occurs upon fast cooling while on slow cooling the disordered phase I is present. Gradual heating from 100 K (phase II) causes the crystal to return to the original phase I at about 150 K. The crystal undergoes the observed transformation in a reversible manner in many consecutive flash cooling/heating cycles without cracking.