Computational UV spectra for amorphous solids of small molecules

Wallace, Austin M.; Fortenberry, Ryan C.

doi:10.1039/d1cp03255k

Cited by 5 publications

(11 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From previous benchmarking on clusters with 8 molecules and CAM-B3LYP/6-311G(d,p), the amorphous spectra predictions for water, ammonia, and carbon dioxide are off from experiment by 0.51, 0.32, and 0.24 eV, respectively. 31 Though such a shift could put the amorphous style clusters more in line with the experiments, such would still likely fall short. However, the amorphous clusters do provide a possible clue as to the origins of lower energy feature in their nonzero oscillator strength n → σ* transitions.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

“…Amorphous carbonic acid is simulated by generating 40 randomized clusters. 31 Each cluster consists of 8 carbonic acid molecules composed of the two lowest energy conformational isomers of the monomer. Previous work has shown that 8 carbonic acid molecules are enough to achieve convergence in the spectra, 20 and the same number produces similar behavior in related carbon dioxide clusters.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

“…Previous work has shown that 8 carbonic acid molecules are enough to achieve convergence in the spectra, 20 and the same number produces similar behavior in related carbon dioxide clusters. 31 Although 30 clusters are composed of the lowest energy syn-syn carbonic acid monomers, 5 clusters are built from the second lowest conformational isomer, syn-anti monomers, and the remaining 5 clusters are a mixture of syn-syn and syn-anti monomers. Incorporating some of the syn-anti monomers provides a more complete sampling of the amorphous structure.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

“…Simultaneously, a new procedure leveraging quantum mechanics and statistical mechanics has been able to generate UV spectra for amorphous water, ammonia, and carbon dioxide in agreement with experiment with a mean absolute error of 3.3% for CAM-B3LYP/6-311G(d,p). 31 Such a procedure is related to ongoing research in polymolecular quantum chemistry, 32,33 and this represents an extension to amorphous solids of astrophysical application. 20,31 Therefore, the present work will utilize this procedure to analyze amorphous carbonic acid clusters' UV spectra to potentially characterize the unknown carbonic acid structure observed in Experimental Solid A.…”

Section: ■ Introductionmentioning

confidence: 99%

“…31 Such a procedure is related to ongoing research in polymolecular quantum chemistry, 32,33 and this represents an extension to amorphous solids of astrophysical application. 20,31 Therefore, the present work will utilize this procedure to analyze amorphous carbonic acid clusters' UV spectra to potentially characterize the unknown carbonic acid structure observed in Experimental Solid A. 8 Additionally, the ribbon structure is investigated further with respect to the Experimental Solid B spectrum, and a new twisted motif for pairs of dimers is also explored to see its relevance to either case.…”

Section: ■ Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Theoretical Characterization of Carbonic Acid Clusters in the UV

Wallace

Fortenberry

2022

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

Two theoretical structural motifs are proposed to match two experimental solid carbonic acid UV spectra from previous literature (Astron. Astrophys. 2021, 646, A172): a linear ribbon structure as a single octamer and nonplanar orientations of carbonic acid clusters. The latter have some contribution from approximated amorphous solid carbonic acid in the form of 40 different clusters of 8 carbonic acid molecules ensemble-averaged together, but unoptimized pairs of optimized dimers oriented perpendicular to one another give the strongest intensities of lower energy UV transitions. The linear ribbon structure's predicted spectrum computed with CAM-B3LYP/6-311G(d,p) agrees well with Experimental Solid Bthe β-carbonic acid experimental data in the UV region. Meanwhile, the 40 amorphous clusters are built with a randomization script, and the electronically excited states are calculated with both CAM-B3LYP/6-311G(d,p) and ωB97XD/ 6-311G(d,p). The resulting theoretical spectrum is constructed by employing a Boltzmann distribution of the intensities and artificially broadening the simulated spectra. The nonplanar dimer pairs are computed with CAM-B3LYP and B3LYP with the 6-311G(d,p) basis set. The results of the amorphous simulation weakly correspond with the Experimental Solid A spectrum, but the fully nonplanar motif matches the experiment much more convincingly. As a result, the previous work appears to have observed the traditional crystalline phase of solid carbonic acid in Experimental Solid B, whereas the nonplanar orientations of the carbonic acids in the clusters appear to correlate with Experimental Solid A. This spectral classification will aid in future laboratory work exploring the role that carbonic acid can play in low temperature, low pressure desorbed environments with potential application to astrochemistry.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 96%

Section: ■ Computational Methodsmentioning

confidence: 99%

Section: ■ Computational Methodsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Theoretical Characterization of Carbonic Acid Clusters in the UV

Wallace

Fortenberry

2022

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

show abstract

Nonlinear optical properties and optimization strategies of D-π-A type phenylamine derivatives in the near-infrared region

Jia

Yang

et al. 2022

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

View full text Add to dashboard Cite

Red-Shifting the Excitation Energy of Carbonic Acid Clusters Via Nonminimum Structures

et al. 2023

Self Cite

View full text Add to dashboard Cite

Nonminimum carbonic acid clusters provide excitation energies and oscillator strengths in line with observed ice-phase UV absorptions better than traditional optimized minima. This equation-of-motion coupled cluster quantum chemical analysis on carbonic acid monomers and dimers shows that shifts to the dihedral angle for the internal heavy atoms in the monomer produce UV electronic excitations close to 200 nm with oscillator strengths that would produce observable features. This τ(OCOO) dihedral is actually a relatively floppy motion unlike what is often expected for sp2 carbons and can be distorted by 30° away from equilibrium for an energy cost of only 11 kcal/mol. As this dihedral decreases beyond 30°, the excitation energies decrease further. The oscillator strengths do, as well, but only to a point. Hence, the lower-energy distortions of τ(OCOO) are sufficient to produce structures that exhibit excitation energies and oscillator strengths that would red-shift observed spectra of carbonic acid ices away from the highest UV absorption feature at 139 nm. Such data imply that colder temperatures (20 K) in the experimental treatment of carbonic acid ices are freezing these structures out after annealing, whereas the warmer temperature experiments (80 K) are not.

show abstract

Computational UV spectra for amorphous solids of small molecules

Abstract: Ices in the interstellar medium largely exist as amorphous solids composed of small molecules including ammonia, water, and carbon dioxide. Describing gas-phase molecules can be readily accomplished with current high-level...

Cited by 5 publications

References 44 publications

Theoretical Characterization of Carbonic Acid Clusters in the UV

Theoretical Characterization of Carbonic Acid Clusters in the UV

Nonlinear optical properties and optimization strategies of D-π-A type phenylamine derivatives in the near-infrared region

Red-Shifting the Excitation Energy of Carbonic Acid Clusters Via Nonminimum Structures

Contact Info

Product

Resources

About