Avoiding Electron Spill-Out in QM/MM Calculations on Excited States with Simple Pseudopotentials

Alireza Marefat Khah*, Peter Reinholdt, Jógvan Magnus Haugaard Olsen, Jacob Kongsted, Christof Hättig

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


QM/MM calculations of electronic excitations with diffuse basis sets often have large errors due to spill-out of electrons from the quantum subsystem. The Pauli repulsion of the electrons by the environment has to be included to avoid this. We propose transferable atomic all-electron pseudopotentials that can readily be combined with most MM force fields to avoid electron spill-out. QM/MM excitation energies computed with time-dependent Hartree-Fock and the algebraic diagrammatic construction through second-order are benchmarked against supermolecular calculations to validate these new pseudopotentials. The QM/MM calculations with pseudopotentials give accurate results that are stable with augmentation of the basis set with diffuse functions. We show that the largest contribution to residual deviations from full QM calculations is caused by the missing London dispersion interaction.

Original languageEnglish
JournalJournal of Chemical theory and Computation
Issue number3
Pages (from-to)1373-1381
Publication statusPublished - 2020

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