Two-body density matrices

M. Rosina, (a) Direct variational calculation of the two-body density matrix (b) On the unique representation of the two-body density matrices corresponding to the AGP wave function (c) The characterization of the exposed points of a convex set bounded by matrix nonnegativity conditions (d) Hermitian operator method for calculations within the particle-hole space in Reduced Density Operators with Applications to Physical and Chemical Systems—II (R. M. Erdahl, ed.), Queen s Papers in Pure and Applied Mathematics No. 40, Queen s University, Kingston, Ontario, 1974, (a) p. 40, (b) p. 50, (c) p. 57, (d) p. 126. 

The one- and two-body density matrices are formed by contraction of the vector coupling coefficients with the left and right eigenvectors of Eq. (10) (assuming CSC = 1)... 

Here, y, and yj are the one- and two-body density matrices, 1a represents the region of space that is allocated to atom A, and V corresponds to the electric potential from the nuclei. 

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