## Abstract

A new method is proposed for a fast evaluation of high-dimensional integrals of potential energy surfaces (PES) that arise in many areas of quantum dynamics. It decomposes a PES into a canonical low-rank tensor format, reducing its integral into a relatively short sum of products of low-dimensional integrals. The decomposition is achieved by the alternating least squares (ALS) algorithm, requiring only a small number of single-point energy evaluations. Therefore, it eradicates a force-constant evaluation as the hotspot of many quantum dynamics simulations and also possibly lifts the curse of dimensionality. This general method is applied to the anharmonic vibrational zero-point and transition energy calculations of molecules using the second-order diagrammatic vibrational many-body Green's function (XVH2) theory with a harmonic-approximation reference. In this application, high dimensional PES and Green's functions are both subjected to a low-rank decomposition. Evaluating the molecular integrals over a low-rank PES and Green's functions as sums of low-dimensional integrals using the Gauss–Hermite quadrature, this canonical-tensor-decomposition-based XVH2 (CT-XVH2) achieves an accuracy of 0.1 cm^{−1} or higher and nearly an order of magnitude speedup as compared with the original algorithm using force constants for water and formaldehyde.

Original language | English (US) |
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Pages (from-to) | 2120-2134 |

Number of pages | 15 |

Journal | Molecular Physics |

Volume | 115 |

Issue number | 17-18 |

DOIs | |

State | Published - Sep 17 2017 |

## Keywords

- Green's function theory
- Potential energy surfaces
- anharmonic vibrations
- tensor decomposition

## ASJC Scopus subject areas

- Biophysics
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry