  A new method for calculation of shell model intrinsic density matrices,
defined as two-particle density matrices integrated over the centre-of-mass
position vector of two last particles and complemented with isospin variables,
has been developed. The intrinsic density matrices obtained are completely
antisymmetric, translation-invariant, and do not employ a group-theoretical
classification of antisymmetric states. They are used for exact realistic
density matrix expansion within the framework of the reduced Hamiltonian
method. The procedures based on precise arithmetic for calculation of the
intrinsic density matrices that involve no numerical diagonalization or
orthogonalization have been developed and implemented in the computer code.
