A-VCI: A flexible method to efficiently compute vibrational spectra

Odunlami, Marc; Bris, Vincent Le; Bégué, Didier; Baraille, Isabelle; Coulaud, Olivier

doi:10.1063/1.4984266

Cited by 26 publications

(39 citation statements)

References 52 publications

(160 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A new VMFCI calculation of all vibrational energy levels of ethylene oxyde up to about 3600 cm −1 has been performed (see supplementary material). The results compare favorably with previously published ones,21,57–59 using the same quartic force field for the nuclear potential. We used the very same force field with AnharmoniCaOs, and compared the results with the VM-FCI ones for different values of the tuning parameters r 3 , r 4 , and h .…”

Section: Resultssupporting

confidence: 87%

Anharmonic vibrational spectroscopy of polycyclic aromatic hydrocarbons (PAHs)

Mulas

Falvo

Cassam-Chenaı̈

et al. 2018

The Journal of Chemical Physics

View full text Add to dashboard Cite

While powerful techniques exist to accurately account for anharmonicity in vibrational molecular spectroscopy, they are computationally very expensive and cannot be routinely employed for large species and/or at non-zero vibrational temperatures. Motivated by the study of Polycyclic Aromatic Hydrocarbon (PAH) emission in space, we developed a new code, which takes into account all modes and can describe all IR transitions including bands becoming active due to resonances as well as overtones, combination and difference bands. In this article, we describe the methodology that was implemented and discuss how the main difficulties were overcome, so as to keep the problem tractable. Benchmarking with high-level calculations was performed on a small molecule. We carried out specific convergence tests on two prototypical PAHs, pyrene (C16H10) and coronene (C24H12), aiming at optimising tunable parameters to achieve both acceptable accuracy and computational costs for this class of molecules. We then report the results obtained at 0 K for pyrene and coronene, comparing the calculated spectra with available experimental data. The theoretical band positions were found to be significantly improved compared to harmonic Density Functional Theory (DFT) calculations. The band intensities are in reasonable agreement with experiments, the main limitation being the accuracy of the underlying calculations of the quartic force field. This is a first step towards calculating moderately high-temperature spectra of PAHs and other similarly rigid molecules using Monte Carlo sampling.

show abstract

Section: Resultssupporting

confidence: 87%

Anharmonic vibrational spectroscopy of polycyclic aromatic hydrocarbons (PAHs)

Mulas

Falvo

Cassam-Chenaı̈

et al. 2018

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…Using several computational methods, it is now possible to compute many numerically exact (ro-)vibrational energy levels and wavefunctions of molecules with 6 or more atoms. [26,66,68,[87][88][89][90][91][92][93][94][95][96][97][98][99][100][101] For molecules with three atoms such calculations are straightforward because it is possible to use a direct product basis composed of products of univariate functions. This simply strategy does not work for larger molecules because the size of the basis scales as n 3N −6 × (2J + 1), where N is the number of atoms in the molecule, n is the number of univariate functions per vibrational coordinate, and J is the angular momentum quantum number.…”

Section: Discussionmentioning

confidence: 99%

Using monomer vibrational wavefunctions to compute numerically exact (12D) rovibrational levels of water dimer

Wang

Carrington

2018

The Journal of Chemical Physics

View full text Add to dashboard Cite

We compute numerically exact rovibrational levels of water dimer, with 12 vibrational coordinates, on the accurate CCpol-8sf ab initio flexible monomer potential energy surface [C. Leforestier et al., J. Chem. Phys. 137, 014305 (2012)]. It does not have a sum-of-products or multimode form and therefore quadrature in some form must be used. To do the calculation, it is necessary to use an efficient basis set and to develop computational tools, for evaluating the matrix-vector products required to calculate the spectrum, that obviate the need to store the potential on a 12D quadrature grid. The basis functions we use are products of monomer vibrational wavefunctions and standard rigid-monomer basis functions (which involve products of three Wigner functions). Potential matrix-vector products are evaluated using the F matrix idea previously used to compute rovibrational levels of 5-atom and 6-atom molecules. When the coupling between inter- and intra-monomer coordinates is weak, this crude adiabatic type basis is efficient (only a few monomer vibrational wavefunctions are necessary), although the calculation of matrix elements is straightforward. It is much easier to use than an adiabatic basis. The product structure of the basis is compatible with the product structure of the kinetic energy operator and this facilitates computation of matrix-vector products. Compared with the results obtained using a [6 + 6]D adiabatic approach, we find good agreement for the inter-molecular levels and larger differences for the intra-molecular water bend levels.

show abstract

“…An other pertinent criteria for subspace selection is the residue. It is widely adopted in Davidson like methods [48,49,50,51] and has recently been implemented in A-VCI [20,21] sharing same structure than the A k decomposition [3]. In the A k theory, one considers primary and secondary spaces respectively called B and B S .…”

Section: State Of the Artmentioning

confidence: 99%

“…Harmonic frequency in cm´1. Correspondence with the ones listed in [21] ν 1 " ω 13 , ν 2 " ω 11 , ν 3 " ω 9 , ν 4 " ω 6 , ν 5 " ω 3 , ν 6 " ω 14 , ν 7 " ω 8 , ν 8 " ω 4 , ν 9 " ω 12 , ν 10 " ω 10 , ν 11 " ω 5 , ν 12 " ω 2 , ν 13 " ω 15 , ν 14 " ω 7 , ν 15 " ω 1 .…”

Section: H 4 O : Ethylene Oxidementioning

confidence: 99%

Dual vibration configuration interaction (DVCI). An efficient factorization of molecular Hamiltonian for high performance infrared spectrum computation

Garnier

2019

Computer Physics Communications

View full text Add to dashboard Cite

Here is presented an original program based on molecular Schrödinger equations. It is dedicated to target specific states of infrared vibrational spectrum in a very precise way with a minimal usage of memory. An eigensolver combined with a new probing technique accumulates information along the iterations so that desired eigenpairs rapidly tend towards the variational limit. Basis set is augmented from the maximal components of residual vectors that usually require the construction of a big matrix block that here is bypassed with a new factorisation of the Hamiltonian. The latest borrows the mathematical concept of duality and the second quantization formalism of quantum theory.Licensing provisions: GNU General Public License 3.Programming languages: C/C++/Fortran. Supplementary materials: 1. The sources of the code grouped in folder DualVCI.zip also available at https: // github. com/ 4Rom1/ DualVCI 2. The input files of examples treated in section 6.Nature of problem: High computational cost in vibration configuration interaction methods [1,2], coming from the necessity to solve a large eigenvalue problem to acquire a good precision. The dimension of the matrix exponentially increases with the size of the studied molecule.Solution method: The A k decomposition [3] completed by a meaningful error evaluation namely the residue ||HX´EX|| minimised along iterations for specific targets given in input. The approximation space is generated in the same time as the residual vectors computed on the fly thanks to an adapted choice of excitations shaped on the Hamiltonian operator.

show abstract

A-VCI: A flexible method to efficiently compute vibrational spectra

Cited by 26 publications

References 52 publications

Anharmonic vibrational spectroscopy of polycyclic aromatic hydrocarbons (PAHs)

Anharmonic vibrational spectroscopy of polycyclic aromatic hydrocarbons (PAHs)

Using monomer vibrational wavefunctions to compute numerically exact (12D) rovibrational levels of water dimer

Dual vibration configuration interaction (DVCI). An efficient factorization of molecular Hamiltonian for high performance infrared spectrum computation

Contact Info

Product

Resources

About