The cumulant expansion is a powerful approach for including correlation effects in electronic structure calculations beyond the $GW$ approximation. However, the expansion is not generally valid, as current implementations ignore terms that mix particle and hole states and lead to partial occupation numbers of one-electron states. These limitations are corrected here using a cumulant expansion of the retarded one-electron Green's function that includes both particle and hole contributions. The approach provides a consistent framework that improves on the $GW$ approximation to the spectral function without additional computational effort. The method is illustrated with results for the homogeneous electron gas and comparisons to experiment and other methods.The cumulant expansion is a powerful approach for including correlation effects in electronic structure calculations beyond the $GW$ approximation. However, the expansion is not generally valid, as current implementations ignore terms that mix particle and hole states and lead to partial occupation numbers of one-electron states. These limitations are corrected here using a cumulant expansion of the retarded one-electron Green's function that includes both particle and hole contributions. The approach provides a consistent framework that improves on the $GW$ approximation to the spectral function without additional computational effort. The method is illustrated with results for the homogeneous electron gas and comparisons to experiment and other methods.

Physical Review BAug 11, 2014106 citations

Cumulant Expansions and Energy Shifts Obtained by Using a Quantum Physical Perturbation

Won Sik L’YI

New Physics Sae MulliJun 30, 20100 citations

Development of density cumulant functional theory

Alexander Yuryevich Sokolov

May 1, 20140 citations

The cumulant expansion is a powerful approach for including correlation effects in electronic structure calculations beyond the

GW

approximation. However, the expansion is not generally valid, as current implementations ignore terms that mix particle and hole states and lead to partial occupation numbers of one-electron states. These limitations are corrected here using a cumulant expansion of the retarded one-electron Green's function that includes both particle and hole contributions. The approach provides a consistent framework that improves on the

GW

approximation to the spectral function without additional computational effort. The method is illustrated with results for the homogeneous electron gas and comparisons to experiment and other methods.