Spin unrestricted calculations using density functional theory can yield wave functions with spin contamination. In conventional post Hartree–Fock calculations ~such as Mo”ller–Plesset perturbation theory!, spin projection can ameliorate some of the problems caused by spin contamination. However, spin projection can seriously degrade the quality of potential energy surfaces calculated by densit...

We describe a hierarchy of approximations (MP2[x]) that allow one to estimate second-order Møller-Plesset (MP2) energies in a large basis set from small-basis calculations. The most cost-effective approximation, MP2[K], is significantly cheaper than full MP2 but numerical tests on small atoms and molecules indicate that it is nonetheless accurate. We conclude that MP2[K] is an attractive level ...

We consider a modified Schrödinger equation wherein the electron-electron repulsion terms r(ij)(-1) are approximated by truncated one-particle resolutions. Numerical results for the He atom and H2 molecule at the Hartree-Fock, second-order Møller-Plesset, and configuration interaction levels show that the solutions of the resulting reduced-rank Schrödinger equations converge rapidly, and that e...

A fast stochastic method for calculating the second order Møller-Plesset (MP2) correction to the correlation energy of large systems of electrons is presented. The approach is based on reducing the exact summation over occupied and unoccupied states to a time-dependent trace formula amenable to stochastic sampling. We demonstrate the abilities of the method to treat systems with thousands of el...

The author introduces a new method for the exchange commutator integrals in explicitly correlated Møller-Plesset second order perturbation theory. The method is well suited with an analytic Slater-type geminal correlation factor. He also explains the scheme for auxiliary integrals needed for the correlation factor. Based on different Ansätze, he analyzes the performance of the method on correla...

A modified version of the Møller-Plesset approach for obtaining the correlation energy associated to a Hartree-Fock ground state is proposed. The method is tested in a model of interacting fermions that allows for an exact solution. Using up to third order terms improved results are obtained, even in the limit of loosely bound particles. Tested in molecules as well, the modified method appears ...

A systematic method for approximating the ab initio electronic energy of crystal lattices has been improved by the incorporation of long range electrostatic and dispersion interactions. The effect of these long range interactions on the optimization of the crystal structure is reported. The harmonic lattice dynamics have been evaluated to give phonon frequencies and neutron scattering intensiti...

We investigate the dynamical spin polarization of a massless electron probing an plasma in locally thermal equilibrium via Moller scattering from quantum kinetic theory. derive axial equation delineating evolution presence collision term with corrections up to $\mathcal{O}(\ensuremath{\hbar})$ and leading-logarithmic order coupling by using hard-thermal-loop approximation, which we extract spin...