This need is firstly opened in pyscf issue pyscf/pyscf#357 . 2-particle spin-orbital density matrices <i_alpha^+ j_alpha^+ k_alpha l_alpha>, <i_alpha^+ j_beta^+ k_beta l_alpha>, <i_beta^+ j_beta^+ k_beta l_beta> are needed to analyze spin correlation function
This need is firstly opened in pyscf issue pyscf/pyscf#357 . 2-particle spin-orbital density matrices <i_alpha^+ j_alpha^+ k_alpha l_alpha>, <i_alpha^+ j_beta^+ k_beta l_alpha>, <i_beta^+ j_beta^+ k_beta l_beta> are needed to analyze spin correlation function