In insulators, Borneffectivecharges describe the electrical polarization induced by the displacement of individual atomic sublattices. Such a physical property is at first sight irrelevant for metals and doped semiconductors, where the macroscopic polarization is ill defined.
The Born effective charge tensors are necessary for computing infrared (IR) intensity for IR-active vibrational modes. 4. Extracting mode symmetries with Phonopy. Files for this section: github link. After performing the DFPT calculation, it is possible to get mode symmetries from the vasprun.xml file generated by VASP
Jul 01, 2022 · The issue with Borneffectivecharge. TDEP enforce the symmetry of the Borneffectivecharge. In the case of SrTiO3, it enforce the Borneffectivecharge to a wrong value. To bypass this issue, I modified the TDEP code to skip the symmetrization of Borneffectivecharge. When I run extract_forceconstant, I need to add a new tag --nosymmborn
This coupling between optical phonons and electric fields is quantified by the Born effective charge, which is defined through. (3.95) i.e. the Born effective charge is the coefficient of proportionality between a change in macroscopic polarisation in direction caused by an atomic displacement in direction under conditions of zero external field.
Borneffectivecharge tensors are used in DFT-VASP  to calculate the dipole moment. The dipole moment of each atom is calculated by ∂d i = Z * ij ∂r j, (1) where Z* ij is the Borneffectivecharge tensors and ∂rj is the displacement. In our case, the displacement is defined corresponding to the flat configuration.. Borneffective ...