Subsystem density-functional theory (DFT) [1] provides an attractive computational approach for treating material built from molecular building blocks. Here, we present our recent progress in applying methods based on subsystem DFT to such molecular materials, focussing on two aspects.<br/><br/>First, we investigate the use of an embedded many-body expansion in order to calculate accurate energy differences between polymorphs of molecular materials. We show that the use of density-based embedding (DFT-in-DFT and wavefunction-in-DFT) can result in a faster convergence of embedded many-body expansions [2].<br/><br/>Second, we show how intermolecular charge transfer in molecular materials can be described within the framework of subsystem DFT. To this end, we extent subsystem DFT to subsystems with fractional electron numbers. Such a formulation can be used to alleviate shortcomings of conventional density-functional approximations by enforcing the correct fractional charge behavior for the embedded subsystems, thus enabling a qualitatively correct description of inter-subsystem charge transfer [3].

Subsystem density-functional theory for molecular materials

2019 Spring National Meeting

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