Advanced concepts within the automated generation of multi-dimensional potential energy surfaces
Final Report Abstract
New programs have been developed, which allow for the very efficient calculation of multidimensional potential energy surfaces (PES) and their transformation into representations, which are advantageous within subsequent vibrational configuration interaction calculations (VCI) for the accurate simulation of molecular vibrational spectra. These programs comprise a code, which is able to handle molecular point group symmetry and permutational symmetry at the same time and thus allows for the exploitation of symmetry within calculations based on coordinate systems including localized normal coordinates. In a set of systematic benchmark calculations it could be shown that the use of localized normal coordinates for small molecules is less beneficial than anticipated. Besides this a new algorithm has been developed, which allows for the very efficient transformation of grid representations of PESs to any analytical reprsentations. This transformation is based on Kronecker products and outperforms standard solvers for linear systems of equations by several orders in magnitude for both, CPU-time and memory demands. As a result, fitting a PES to polynomials, B-splines or distributed Gaussians essentially takes no time for low orders of an n-mode expansion of a PES. A third program has been developed, which enables a tensor decomposition of high-order terms of an n-mode representation of a PES once it is expressed in terms of local basis function, e.g. B-splines or distributed Gaussians. It could be shown that high accuracy can be achieved, but the computation time for the decomposition still overcompensates the gain of CPU-time in the subsequent VCI calculations. Consequently, new decomposition schemes need to be developed with a lower operation count. The new programs have been applied to molecules of current research, often in support of experiments performed by collaboration partners. This comprises molecules as H2 NNO, B2 H6 , CH3 OPO, CH3 PO2 , HCCNCO, C2 H6 and C2 H5 F and isotopologues of these species. The efficient calculation of PESs at the level of explicitly correlated coupled-cluster theory became only feasible due to the new programs and very high accuracy has been obtained in all cases, which allowed to guide the analysis of the experimentally obtained spectra.
Publications
- Efficient generation of sum-of-products representations of high-dimensional potential energy surfaces based on multimode expansions. J. Chem. Phys. 144, 114114 (2016)
B. Ziegler and G. Rauhut
(See online at https://doi.org/10.1063/1.4943985) - Tensor decomposition in potential energy surface representations. J. Chem. Phys. 145, 104103 (2016)
L. Ostrowski, B. Ziegler and G. Rauhut
(See online at https://doi.org/10.1063/1.4962368) - Rigorous use of symmetry within the construction of multidimensional potential energy surfaces. J. Chem. Phys. 149, 164110 (2018)
B. Ziegler and G. Rauhut
(See online at https://doi.org/10.1063/1.5047912) - Accurate Vibrational Configuration Interaction Calculations on Diborane and Its Isotopologues. J. Phys. Chem. A 123, 3367-3373 (2019)
B. Ziegler and G. Rauhut
(See online at https://doi.org/10.1021/acs.jpca.9b01604) - Localized Normal Coordinates in Accurate Vibrational Structure Calculations: Benchmarks for Small Molecules. J. Chem. Theory Comput. 15, 4187-4196 (2019)
B. Ziegler and G. Rauhut
(See online at https://doi.org/10.1021/acs.jctc.9b00381) - Phosphorus Analogues of Methyl Nitrite and Nitromethane: CH3 OPO and CH3 PO2. Angew. Chem. Int. Ed. 58, 12164-12169 (2019)
X. Zhao, X. Chu, G. Rauhut, C. Chen, C. Song, B. Lu, and X. Zeng
(See online at https://doi.org/10.1002/anie.201906874) - The Simplest but Isolable Alkynyl Isocyanate HCCNCO. Angew. Chem. Int. Ed. 58, (2019)
Y. Qin, B. Lu, G. Rauhut, M. Hagedorn, K. Banert, C. Song, X. Chu, L. Wang and X. Zeng
(See online at https://doi.org/10.1002/ange.201911102) - Vibrational analysis of nitrosamine, a molecule with an almost constant potential along the inversion coordinate. Mol. Phys. 117, 1741-1745 (2019)
B. Ziegler and G. Rauhut
(See online at https://doi.org/10.1080/00268976.2018.1522004)
