Niemeyer N, Neugebauer J. Response properties from frozen-density embedding approximate second-order coupled-cluster theory.
J Chem Phys 2025;
162:174110. [PMID:
40314269 DOI:
10.1063/5.0260850]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2025] [Accepted: 04/07/2025] [Indexed: 05/03/2025] Open
Abstract
We present an implementation of the coupled frozen-density embedding (FDEc) formalism for the calculation of ground-state and excited-state properties, linear-response properties, and transition moments with the coupled cluster with the singles and approximate doubles (CC2) model. Following the general strategy introduced by Höfener and Visscher [J. Chem. Theory Comput.12, 549-557 (2016)], we derive the working equations needed for the evaluation of these properties and describe their implementation into our open-source quantum chemistry program, Serenity. Our implementation comprises both projection-based embedding as well as embedding based on non-additive kinetic-energy functionals and the corresponding potentials. It makes use of the resolution-of-the-identity technique and features-in addition to CC2-the algebraic diagrammatic construction scheme of second order, ADC(2), as well as spin-component-scaled and scaled-opposite spin versions of CC2 and ADC(2). We demonstrate the capabilities of this FDEc framework by analyzing excitation energies, singlet and triplet excitation-energy splittings as well as oscillator strengths of excitonically coupled dimers, the excited-state/difference dipole moment of a formaldehyde⋯water system, and the optical rotatory dispersion of a microsolvated organic chromophore. In the latter case, we reconsider the case of (P)-dimethylallene· (H2O)2, for which uncoupled CC2-based frozen-density embedding fails, while FDEc-time-dependent density-functional theory showed promising results in earlier work. Here, we can confirm that the inclusion of system-environment response couplings leads to agreement with supermolecular CC2 results, highlighting the importance of inter-subsystem couplings in response-property calculations for molecular aggregates.
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