Vibrational excitation energies from vibrational coupled cluster response theory

Seidler, Peter; Christiansen, Ove

doi:10.1063/1.2734970

Cited by 89 publications

(82 citation statements)

References 37 publications

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“…12,24 In this spirit we now introduce hybrid optimized and localized coordinates (HOLCs) that attempt to establish a good compromise between localized and optimized coordinates.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Optimized and Localized Vibrational Coordinates

2015

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We present a new type of vibrational coordinates denoted hybrid optimized and localized coordinates (HOLCs) aiming at a good set of rectilinear vibrational coordinates supporting fast convergence in vibrational stucture calculations. The HOLCs are obtained as a compromise between the recently promoted optimized coordinates (OCs) and localized coordinates (LCs). The three sets of coordinates are generally different from each other and differ from standard normal coordinates (NCs) as well. In determining the HOLCs, we optimize the vibrational self-consistent field (VSCF) energy with respect to orthogonal transformation of the coordinates, which is similar to determining OCs but for HOLCs we additionally introduce a penalty for delocalization, by using a measure of localization similar to that employed in determining LCs. The same theory and implementation covers OCs, LCs, and HOLCs. It is shown that varying one penalty parameter allows for connecting OCs and LCs. The HOLCs are compared to NCs, OCs, and LCs in their nature and performance as basis for vibrational coupled cluster (VCC) response calculations of vibrational anharmonic energies for a small set of simple systems comprising water, formaldehyde, and ethylene. It is found that surprisingly good results can be obtained with HOLCs by using potential energy surfaces as simple as quadratic Taylor expansions. Quite similar coordinates are found for the already established OCs but obtaining these OCs requires much more elaborate and expensive potential energy surfaces and localization is generally not guaranteed. The ability to compute HOLCs for somewhat larger systems is demonstrated for coumarin and the alanine quadramer. The good agreement between HOLCs and OCs, together with the much easier applicability of HOLCs for larger systems, suggests that HOLCs may be a pragmatically very interesting option for anharmonic calculations on medium to large molecular systems.

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“…12,24 In this spirit we now introduce hybrid optimized and localized coordinates (HOLCs) that attempt to establish a good compromise between localized and optimized coordinates.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Optimized and Localized Vibrational Coordinates

2015

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“…VCI approaches on the other hand suffer from the increasing size of the correlation space which of course depends on the quality of the basis functions ͑e.g., statespecific versus ground-state based VSCF modals͒. Several years ago Prasad and co-workers, 10,11 and later on Christiansen and co-workers, 12,13 implemented vibrational coupled-cluster ͑VCC͒ approaches and linear response methods for the first time. Experience with these methods is still limited.…”

Section: Introductionmentioning

confidence: 99%

Vibrational multiconfiguration self-consistent field theory: Implementation and test calculations

Heislbetz

Rauhut

2010

The Journal of Chemical Physics

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A state-specific vibrational multiconfiguration self-consistent field (VMCSCF) approach based on a multimode expansion of the potential energy surface is presented for the accurate calculation of anharmonic vibrational spectra. As a special case of this general approach vibrational complete active space self-consistent field calculations will be discussed. The latter method shows better convergence than the general VMCSCF approach and must be considered the preferred choice within the multiconfigurational framework. Benchmark calculations are provided for a small set of test molecules.

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“…As these operators depend on the modals as well, these equations have to be solved iteratively until self-consistency has been achieved. Once the modals have been determined within the VSCF formalism, vibration correlation effects can be accounted for by different approaches [21,[32][33][34][35]. Due to the direct occurence of many-mode operators in the Watson Hamiltonian significantly higher excitation levels are needed than in electronic structure theory in order to obtain accurate vibrational state energies.…”

Section: Introductionmentioning

confidence: 99%