01255nas a2200169   4500008004100000245009400041210006900135260000800204300002700212490000800239520062800247100001900875700002100894700002100915700002600936856012300962       2009                        eng d00aStudy of cumulant approximations to n-electron valence multireference perturbation theory0 aStudy of cumulant approximations to nelectron valence multirefer  cMAY  aArticle Number: 1941070 v1303 aWe investigate the possibility of reducing the complexity of multireference perturbation theory through cumulant based approximations to the high-order density matrices that appear in such theories. Our test cases show that while the cumulant approximated forms are degraded in accuracy relative to the parent theory and exhibit intruder state problems that must be carefully handled, they may provide a route to a simple estimation of dynamic correlation when the parent perturbation theory is infeasible. Nonetheless, further work is clearly needed on better approximations to the denominators in the perturbation theory.1 aZgid, Dominika1 aGhosh, Debashree1 aNeuscamman, Eric1 aChan, Garnet, Kin-Lic  uhttps://library.ncl.res.in/content/study-cumulant-approximations-n-electron-valence-multireference-perturbation-theory