Tutorial on calculating phonons: comparing the linear response and the small displacement methods
نویسنده
چکیده
1 Phonons in a crystal Consider a crystal at very low temperature and expand the potential energy function around the equilibrium positions of the nuclei. The first term of the expansion is simply the energy of the system calculated with the ions in their equilibrium positions, Eperf . If the crystal is near its minimum energy configuration the linear term of the expansion is zero, and the first term is a quadratic term in the atomic displacements:
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تاریخ انتشار 2007