High-pressure X-ray-diffraction study of α-AlPO<SUB>4</SUB>

Our high-pressure X-ray diffraction experiments on berlinite AlPO4(&#945;-AlPO4) show that it transforms to a crystalline Cmcm phase beyond 13 GPa. The persistence of diffraction pattern up to 40 GPa does not confirm the previous conclusions of high-pressure amorphization of AlPO4 around 12-18 GPa. Our experimental results, in agreement with earlier Raman scattering results, suggest that the so called memory glass effect observed earlier may in fact be due to the reversibility of &#945;-phase Cmcm phase transformation. These new experimental observations raise serious doubts about the theoretical understanding of the high-pressure behavior of &#945;-AlPO4