BORN

When imposing non-analytical term to dynamical matrix, Born effective charges and permittivity read from this file. In fropho, the non-analytical term is implemented following Eq. (3.20) that is given in atomic unit. The first line is the factor that the non-analytical term is multiplied with, and this value is used to adjust the unit system, i.e., if you use VASP code, you have to change the unit system from atomic unit to eV and Å, which might be $27.2116\times 0.52918$. The dielectric constant written in the second line. The continuous lines are the Born effective charges of independent atoms which are displaced. One line represents one Born effective charge tensor. The order of the lines of the permittivity and Born effective charge is given by xx, xy, xz, yx, yy, yz, zx, zy, zz in Cartesian coordinates. The matrix elements in each tensor should be symmetrized by your hand. The number of effective charges (lines) required is determined by fropho. It is easy to check by dry-run, e.g., NDIM = 1 1 1, LSUPER = .TRUE. and IRPINT = 2, and see the line ``independent atom'' in standard output.

example

	14.400
	 2.00  0.00  0.00   0.00  2.00  0.00   0.00  0.00  2.00
	 1.98  0.00  0.00   0.00  1.98  0.00   0.00  0.00  1.98
	-0.99  0.00  0.00   0.00 -0.99  0.00   0.00  0.00 -0.99
	...