The density matrix renormalization group (DMRG) is a powerful method to treat static correlation. Here we present an inexpensive way to calculate correlation energy starting from a DMRG wave function using pair-density functional theory (PDFT). We applied this new approach, called DMRG-PDFT, to study singlet-triplet gaps in polyacenes and polyacetylenes that require active spaces larger than the feasibility limit of the conventional complete active-space self-consistent field (CASSCF) method. The results match reasonably well with the most reliable literature values and have only a moderate dependence on the compression of the initial DMRG wave function. Furthermore, DMRG-PDFT is significantly less expensive than other commonly applied ways of adding additional correlation to DMRG, such as DMRG followed by multireference perturbation theory or multireference configuration interaction.
|Original language||English (US)|
|Number of pages||8|
|State||Published - 2019|
Bibliographical noteFunding Information:
This work was supported in part by Air Force Office of Scientic Research grant FA9550-16-1-0134. SK thanks Markus Reiher (ETH Zürich) for his continuous support.
© 2019 The Royal Society of Chemistry.