Implementation of Surjan's density matrix formulae for calculating second-order Moller-Plesset energy

We numerically assess the method for obtaining second-order Moller-Plesset (MP2) energy from the Hartree-Fock density matrix (DM) recently proposed by Surjan [Surjan, Chem. Phys. Lett. 406 (2005) 318]. It is confirmed that Surjan's method, referred to as DM-Laplace MP2, can obtain MP2 energy accurately by means of appropriate integral quadrature and a matrix exponential evaluation scheme. Numerical tests reveal that the Euler-Maclaurin and the Romberg numerical integration schemes can achieve milli-hartree accuracy with small quadrature points. This Letter also indicates the possibility of the application of DM-Laplace MP2 to linear-scaling self-consistent field techniques, which give approximate DM. (c) 2006 Elsevier B.V. All rights reserved.