One approach to calculating electronic excited states treats both ground and excited states as single determinants, either by direct optimization or with the aid of constraints. In this work, we exten...

We investigate the ability of Aufbau suppressed coupled cluster theory to act as a post-linear-response correction to widely used linear response methods for electronically excited states. We find that the theory is highly resilient to shortcomings in the underlying linear response method, with final results from less accurate starting points nearly as good as those from the best starting points. This pattern is especially stark in charge transfer states, where the approach converts starting points with multi-eV errors into post-linear-response results with errors on the order of 0.1 eV. These findings highlight the ability of Aufbau suppressed coupled cluster to perform its own orbital relaxations and raise the question of whether initializing it with an orbital relaxed reference is worth the trouble.

Progress in the fundamental understanding of the chirality-induced spin-selectivity (CISS) effect is hindered by complexity of the systems that have been characterized experimentally. With the goal of...

2024-2025 Diversity Enhancement Faculty Award This award recognizes a faculty member from within The Ohio State University College of Arts and Sciences whose research, teaching and/or service/outreach...

The symmetry breaking in octahedral silsesquioxane and its germanium analogues (Si8O12H8 and Ge8O12H8) has been investigated using the M06-2X/6-31++G(3df, 3pd) method and group theory. Both structures...

Exciton coupling in organic chromophores is revisited through the lens of the transition density. The presented formalism gives insight into the strength and sign of the coupling based on the relativ...

The terminal alkyne C≡C stretch has a large Raman scattering cross section in the “silent” region for biomolecules. Experimental work taking advantage of this property provide an impetus for the development of theoretical tools addressing the vibration. In prior work, we have developed a localized normal mode method for computing terminal alkyne vibrational frequencies using a discrete variable representation of the potential energy surface. Using this method and molecular dynamics simulations, we interpret the unusually broad Raman spectrum of alkynes solvated in triethylamine. Energy decomposition analysis is performed on alkyne-triethylamine dimers to determine that charge transfer, electrostatics, and Pauli repulsion have large effects on the frequency. Molecular dynamics simulations of triethylamine-solvated alkynes are performed and uncover that the terminal alkyne hydrogen interacts strongly with the triethylamine nitrogen. Interactions persist for 3–10 ps. Using this data, a spectroscopic map for terminal alkynes is developed and used to compute Raman spectra for alkynes in triethylamine. We find that the broad experimental spectra result from the combination of a population of alkynes associated with the solvent nitrogens and a population not associated with those nitrogens. This work sets the stage for investigations of alkynes in more complex environments like proteins and nanomaterial surfaces.

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Redox processes are an important step in many chemical and biochemical reactions. One simple approach to calculate the free energy change of a redox process is linear response approximation (LRA). However, variability in conformational and energy-gap sampling poses a challenge in balancing computational cost and accuracy. Herein, we calculate the redox properties of the one-electron oxidation processes for small, biologically relevant redox-active molecules (e.g., phenol, phenolate, benzene, indole, lumiflavin) in aqueous solution using two conformational sampling strategies. We sampled the conformations using molecular mechanics (MM) and hybrid quantum mechanics/molecular mechanics (QM/MM) simulations to investigate how these techniques affect redox properties. We also performed QM/MM energy-gap sampling while varying the QM region to investigate its impact on overall redox behavior. We observed free energy of oxidation, and consequently, oxidation potential differs consistently by ∼0.2–0.4 V between QM/MM and MM sampling for the molecules under investigation. Overall, we infer that computationally cheaper MM sampling would be adequate for computing the redox properties of small molecules when corrected by a system-specific correction factor.

With the advancement of artificial intelligence-embedded methodologies, their application to predict fundamental molecular properties has become increasingly prevalent. In this study, a graph convolut...

Accurate prediction of barrier heights and reaction energies is of paramount importance for reaction kinetics. For computational efficiency, such calculations are typically performed with density func...