Jiawang Hong, David Vanderbilt
We investigate the oxygen octahedral rotations that occur in two perovskites, SrTiO$_3$ and PbTiO$_3$, as a function of applied three-dimensional electric displacement field, allowing us to map out the phase diagram of rotations in both the paraelectric and ferroelectric regions of the polar response. First-principles calculations at fixed electric displacement field are used to extract parameters of a Landau-Devonshire model that is analyzed to identify the phase boundaries between different rotational states. The calculations reveal a rich phase diagram of rotations versus applied field in both SrTiO$_3$ and PbTiO$_3$, although the details are quite different in the two cases.
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http://arxiv.org/abs/1212.0608
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