Quantum mechanical embedding theory based on a unique embedding potential

Abstract

We remove the nonuniqueness of the embedding potential that exists in most previous quantum mechanical embedding schemes by letting the environment and embedded region share a common embedding (interaction) potential. To efficiently solve for the embedding potential, an optimized effective potential method is derived. This embedding potential, which eschews use of approximate kinetic energy density functionals, is then used to describe the environment while a correlated wavefunction (CW) treatment of the embedded region is employed. We first demonstrate the accuracy of this new embedded CW (ECW) method by calculating the van der Waals binding energy curve between a hydrogen molecule and a hydrogen chain. We then examine the prototypical adsorption of CO on a metal surface, here the Cu(111) surface. In addition to obtaining proper site ordering (top site most stable) and binding energies within this theory, the ECW exhibits dramatic changes in the p-character of the CO 4σ and 5σ orbitals upon adsorption that agree very well with x-ray emission spectra, providing further validation of the theory. Finally, we generalize our embedding theory to spin-polarized quantum systems and discuss the connection between our theory and partition density functional theory.

Accurate Reference Data for the Nonadditive, Noninteracting Kinetic Energy in Covalent Bonds

“…This minimization requirement ensures a unique solution and also ends up causing all the fragment embedding potentials to be equal to a single global embedding potential (referred to as the partition potential). Huang et al also use a reformulated version of subsystem-DFT with unique fragment densities based around constraining all fragment embedding potentials to be equal [7]. For both of these methods the fragment densities are uniquely determined both when the exact and approximate NAKE functionals are used.…”

“…These studies are capable of reproducing Kohn-Sham energies and densities via fragment calculations, with primarily two different goals in mind. First the corresponding NAKE functional derivatives or non-additive kinetic potentials (NAKPs) are critical ingredients in embedding potentials which allow higher level wavefunction methods to be approximately combined with KS-DFT calculations [7,8], thus improving upon the accuracy of KS density functional approximations for some small region of interest within a larger system.…”

Accurate basis set truncation for wavefunction embedding

“…Among these are the QM/MM, [1][2][3][4][5][6] ONIOM, 7,8 fragment molecular orbital (FMO), [9][10][11][12][13][14][15] and wavefunction theory (WFT)-in-density functional theory (DFT) embedding [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] approaches, which allow for the treatment of systems that would not be practical using conventional WFT approaches. In particular, WFT-in-DFT embedding utilizes the theoretical framework of DFT embedding to enable the WFT description of a given subsystem in the effective potential that is created by the remaining electronic density of the system.…”

Communication: Dynamical embedding: Correct quantum response from coupling TDDFT for a small cluster with classical near-field electrodynamics for an extended region

“…14 (For other approaches see Refs. [15][16][17][18][19][20] Our approach describes nanostructures as quantum systems embedded within a frequency-dependent dielectric medium; the systems are propagated simultaneously, coupled through an overall time-dependent potential. The method was demonstrated on a one-dimensional jellium system.…”