A first-principles scheme to phonons of high temperature phase: Noimaginary modes for cubic SrTiO

摘要

The issue of imaginary phonon modes predicted by first-principles calculations for high-temperaturenstructures of most materials has been a longstanding problem for decades. We propose that thenobserved high-temperature structures are actually dynamic averages of related low-temperaturenstructures. This theory is used to predict the phonon dispersions of cubic SrTiO3. The calculatednphonon dispersions for the cubic phase, using the force constants calculated from the tetragonalnphases, are found to be in remarkably good agreement with existing neutron data, without exhibitingnany imaginary phonon modes. © 2010 American Institute of Physics. u0004doi:10.1063/1.3505338