*Distortions in simple-cubic calcium at high pressure
Scientists led by Wendy Mao, Stanford University, made a surprising discovery in research involving Ca-III, Research reveals a scenario that the "high-pressure structure of calcium does not go to the zero-temperature global enthalpy minimum but is dictated by high-temperature anharmonicity and low-temperature metastability fine-tuned with phonon stability at the local minimum." Ca-III, the first superconducting calcium phase under pressure, sustains a rhombohedral distortion at 300 K and a monoclinic distortion below 30 K.
Please see the article: W. L. Mao, L. Wang, Y. Ding, W. Yang, W. Liu, D. Y. Kim, W. Luo, R. Ahuja, Y. Meng, S. V. Sinogeikin, J. Shu, and H-k. Mao, Distortions in Simple-cubic Calcium at High Pressure, Proc. Nat. Acad. Sci. USA, 107:22, 9965-9968 (2010). doi: 10.1073/pnas.1005279107.