Quartic force fields (QFFs) constructed using a sum of ground-state CCSD(T)-F12b energies with EOM-CCSD excitation energies are proposed for computation of spectroscopic properties of electronically excited states. This is dubbed the F12+EOM approach and is shown to provide similar accuracy to previous methodologies at lower computational cost. Using explicitly correlated F12 approaches instead of canonical CCSD(T), as in the corresponding (T)+EOM approach, allows for 70-fold improvement in computational time. The mean percent difference between the two methods for anharmonic vibrational frequencies is only 0.10%. A similar approach is also developed herein which accounts for core correlation and scalar relativistic effects, named F12cCR+EOM. The F12+EOM and F12cCR+EOM approaches both match to within 2.5% mean absolute error of experimental fundamental frequencies. These new methods should help in clarifying astronomical spectra by assigning features to vibronic and vibrational transitions of small astromolecules when such data are not available experimentally.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1021/acs.jpca.3c00072 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Computing Accurate & Reliable Rovibrational Spectral Data for Aluminum-Bearing Molecules.
J Comput Chem
January 2025
Department of Chemistry and Biochemistry, University of Mississippi, Oxford, Mississippi, USA.
The difficulty of quantum chemically computing vibrational, rotational, and rovibrational reference data via quartic force fields (QFFs) for molecules containing aluminum appears to be alleviated herein using a hybrid approach based upon CCSD(T)-F12b/cc-pCVTZ further corrected for conventional CCSD(T) scalar relativity within the harmonic terms and simple CCSD(T)-F12b/cc-pVTZ for the cubic and quartic terms: the F12-TcCR+TZ QFF. Aluminum containing molecules are theorized to participate in significant chemical processes in both the Earth's upper atmosphere as well as within circumstellar and interstellar media. However, experimental data for the identification of these molecules are limited, showcasing the potential for quantum chemistry to contribute significant amounts of spectral reference data.
View Article and Find Full Text PDFIn this Letter, we investigate the binding mechanism and motion dynamics of the bound state consisting of two pure-quartic solitons (PQSs) with unequal intensities and find that their movement occurs as an entity under the Raman self-frequency shift. By calculating the forces that induce the relative motion between the unequal PQSs, we derive the balanced conditions for maintaining a near-constant separation and the constant phase profile between them. The predictions are validated by the numerical simulations.
View Article and Find Full Text PDFNonlinear resonance in an overdamped Duffing oscillator as a model of paleoclimate oscillations.
Phys Rev E
September 2024
Max Planck Institute for the Physics of Complex Systems, Dresden 01187, Germany.
The cause of the dominant 100-kyr cycles in Earth's paleoclimate in the last 800 000 years has since long been debated. We analyze geological temperature proxy data and retrieve an anharmonic potential from time series data. The obtained potential has bistable features but has significant differences compared to the quartic potentials derived from theoretical energy-based models.
View Article and Find Full Text PDFVibrational and Rovibrational Spectroscopic Data for the Ground and First-Excited States of Phosgene (COCl), Formic Acid (HCOOH), and Chloroformic Acid (ClCOOH).
J Phys Chem A
September 2024
Department of Chemistry & Biochemistry, University of Mississippi, University, Mississippi 38677-1848, United States.
While "black box" quantum chemical computations for the determination of rovibronic spectral data are not quite at hand, the present work utilizes the titular molecules to showcase how excited-state quantum chemical methods can be conjoined to quartic force field (QFF) anharmonic rovibrational treatments to provide novel and useful predictions for such data. This work employs hybrid QFFs with explicitly correlated coupled cluster theory along with the equation-of-motion formalism to generate harmonic force constants and time-dependent density functional theory (TD-DFT) to produce anharmonic force constants for the generation of electronically excited-state rovibrational spectral data, in effect, rovibronic spectral data. Specific spectroscopic results from this work show that the fundamental C═O stretch in phosgene as well as in - and -formic acid drop from the region of around 1800 cm to close to 1100 cm or less in the first excited states of each molecule.
View Article and Find Full Text PDFThe fundamental vibrational frequencies and spectroscopic constants of the COH isomers: molecules known in simulated interstellar ice analogues.
Phys Chem Chem Phys
August 2024
University of Mississippi, University, MS, USA.
While -glyoxal may not be easily observable in astronomical sources through either IR or radioastronomy due to its symmetry, its conformer along with the -HCOCO epoxide isomer should be ready targets for astrochemical detection. The present quantum chemical study shows that not only are both molecular isomers strongly polar, they also have notable IR features and low isomerisation energies of 4.1 kcal mol and 10.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!