Theoretical rotation-vibration spectrum of thioformaldehyde

Abstract

We present a variational calculation of the first comprehensive T = 300 K rovibrational line list for thioformaldehyde, H2CS. It covers 41,809 rovibrational levels for states up to J(max) = 30 with vibrational band origins up to 5000 cm(-1) and provides the energies and line intensities for 547,926 transitions from the ground vibrational state to these levels. It is based on our previously reported accurate ab initio potential energy surface and a newly calculated ab initio dipole moment surface. Minor empirical adjustments are made to the ab initio equilibrium geometry to reduce systematic errors in the predicted intra-band rotational energy levels. The rovibrational energy levels and transition intensities are computed variationally by using the methods implemented in the computer program TROVE. Transition wavelengths and intensities are found to be in excellent agreement with the available experimental data. The present calculations correctly reproduce the observed resonance effects, such as intensity borrowing, thus reflecting the high accuracy of the underlying ab initio surfaces. We report a detailed analysis of several vibrational bands, especially those complicated by strong Coriolis coupling, to facilitate future laboratory assignments.

Ab initio computational spectroscopy and vibrational dynamics of polyatomic molecules: Applications to syn and anti-CH3CHOO and NO3

“…There has also been substantial progress in achieving this goal for general tetraatomics, see for example Refs. [5][6][7][8] and for some larger, albeit semi-rigid molecules, such as CH 4 [9,10], C 2 H 4 [11,12] and CH 3 OO [13]. There has also been significant progress in developing global, i.e., describing multiple minima and in some cases fragment channels, PESs for tetraatomics, based on strict mathematical fitting of tens of thousands of high-level electronic energies.…”

ExoMol line lists – VIII. A variationally computed line list for hot formaldehyde

“…We use an ab initio DMS computed at the CCSD(T)/aug-cc-pVQZ level of theory in the frozen-core approximation using CFOUR (Harding et al 2008). Three symmetry-adapted projections of the dipole moment Cartesian components, µA 1 , µB 1 , and µB 2 , are given in the analytical representations with each component expanded in Taylor series (185 parameters in total) in terms of internal coordinates around the equilibrium configuration using the form developed by Yachmenev et al (2013) to represent the dipole moment of H2CS. These parameters reproduce the ab initio dipole moment values of the µA 1 , µB 1 , and µB 2 components with rms errors of 0.0002 Debyes for each component.…”

The ELPA library: scalable parallel eigenvalue solutions for electronic structure theory and computational science

“…Many of its present users come from a wide range of other electronic structure packages (examples include cp2k, [36] VASP, [37,38] Quantum Espresso, [39] and others). Perhaps the largest documented application of ELPA is the computation of molecular rotation-vibration spectra using the computer program TROVE [40], allowing them to handle matrix sizes beyond 200,000. ELPA is also included directly in Linux distributions such as Debian or Fedora.…”