Phys. Rev. Lett. 89, 115503 (2002) [4 pages]First-Principles Study of the Temperature-Pressure Phase Diagram of BaTiO3Received 23 April 2002; published 23 August 2002 We investigate the temperature-pressure phase diagram of BaTiO3 using a first-principles effective-Hamiltonian approach. We find that the zero-point motion of the ions affects the form of the phase diagram dramatically. Specifically, when the zero-point fluctuations are included in the calculations, all the polar (tetragonal, orthorhombic, and rhombohedral) phases of BaTiO3 survive down to 0 K, while only the rhombohedral phase does otherwise. This behavior results from a practical equivalence between thermal and quantum fluctuations. Our work confirms the essential correctness of the phase diagram proposed by Ishidate et al. [ Phys. Rev. Lett. 78 2397 (1997)]. © 2002 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.89.115503
DOI:
10.1103/PhysRevLett.89.115503
PACS:
61.50.Ks, 61.66.Hq, 64.70.–p, 77.80.Bh
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