  In this paper there is presented method for ab initio calculation of the
phonon spectra. The method is based upon a direct calculation of the dynamical
matrix via second derivatives of the total energy. The pseudopotential
technique in plane-wave basis set was used to calculate the total energy within
the local density approximation (LDA). For the change of the electron density
there is derived the self-consistent equation which is solved analytically with
no use of iterations. In this paper the attention is paid only to non-metallic
systems.
