The computational simulation of the dielectric response of materials is essential for both
analyzing experimental spectra and developing new materials. To accurately calculate the
dielectric function, the classical static charge is often insufficient, and the Born effective
charges or the mass center of the Wannier function (Wannier center) are required to
describe the dipole moments of a system.
For crystals, where the Born effective charges are used to calculate dipoles, we have
combined the self-consistent phonon method [1] and the linear response theory to predict
the dielectric function of highly anharmonic crystals. I will present the accuracy of our
method through applications to strongly anharmoic rutile TiO2 [2].
For liquids, anharmonic phonon methods are not available, and one resorts to molecular
dynamics (MD) simulations. To calculate the system dipoles efficiently and accurately,
we have extended the previously proposed method predicting molecular dipoles [3] and
developed a versatile machine-learning model of dipole moments predicting the Wannier
centers assigned to the chemical bonds [4]. In this talk, I will present the applications to
several liquid alcohols and discuss their dielectric properties.
[1] T. Tadano and S. Tsuneyuki, Phys. Rev. B 92, 054301 (2015).
[2] T. Amano, T. Yamazaki, R. Akashi, T. Tadano, and S. Tsuneyuki, Phys. Rev. B 107, 094305 (2023).
[3] A. Krishnamoorthy, K. Nomura, N. Baradwaj, K. Shimamura, et al, Phys. Rev. Lett. 126, 216403 (2021).
[4] T. Amano, T. Yamazaki, and S. Tsuneyuki, in preparation.

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