Phonon non-analytical term correction

The non-analytical term correction (NAC) corrects the dynamical matrices using (Baroni, 2001, p527; Zhang et al., 2022),

where the denotes the Born effective charge and denotes the dielectric constant.

In phonopy, this is achieved by performing a separate VASP run with LEPSILON = .TRUE. and a denser -mesh to calculate the and , then use phonopy-vasp-born to post-process and create a BORN file.