The subroutine write_eigenvalue contains the several
subroutines to solve dynamical matrices repeatedly along with the list
of Q-points. What we should know is the extended supercell. The
extended supercell is the supercell with the circumference and the
center of the extended supercell is the focused atom where an element
of a dynamical matrix is calculated. The extended supercell is used to
balance the force constant weight.