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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Support for the American Conference on Theoretical Chemistry 2022

The 2022 American Conference on Theoretical Chemistry (ACTC) took place July 25 – July 28 at The Village at Palisades Tahoe in Palisades Tahoe, California (formerly Squaw Valley). The Chair and Vice-Chair of the conference were Todd Martínez (SLAC National Accelerator Laboratory) and David Beratan (Duke University), respectively, and the Deputy Chairs and Local Organizers were Edward Hohenstein (SLAC National Accelerator Laboratory) and Sergey Varganov (University of Nevada, Reno). Held every three years since 1972, the ACTC plays a vital role in presenting pioneering research to a diverse audience in theoretical and computational chemistry. The ACTC 2022 brought together 27 invited speakers who are at the forefront of the field, and provided opportunities for about 150 junior scientists and graduate students to present their work in poster format and exchange ideas with leaders in the field. The funds provided by this DOE award were used to defray $100 of the registration costs for the first registered 98 graduate students and postdoctoral scholars attending the conference. The DOE support was acknowledged on the ACTC 2022 web page (https://sites.google.com/view/actc2022/home) and on a slide that was shown during Conference Introduction and breaks between talks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Multidisciplinary research in space sciences and engineering with emphasis on theoretical chemistry

A broad program is reported of research in theoretical chemistry, particularly in molecular quantum and statistical mechanics, directed toward determination of the physical and chemical properties of materials, relation of these macroscopic properties to properties of individual molecules, and determination of the structure and properties of the individual molecules. Abstracts are presented for each research project conducted during the course of the program.

Hirschfelder, J. O.↗
DOE OSTI2025

Support for the 2024 American Conference on Theoretical Chemistry (ACTC) (Final Report)

Funds are requested in support of the 2024 American Conference on Theoretical Chemistry. Funds are being requested from the Department of Energy in support of conference registration fees for graduate student and post-doctoral researcher registration fees. This conference will be held in North Carolina, and between 200 and 250 participants are expected. This is the major North American meeting of theoretical chemists, showcasing diverse developments in all aspects of modern theory, including methods development and applications. Applications span all aspects of chemistry, biochemistry, and materials science, including important applications to energy science. The conference will include four days of seminars and poster sessions. As well as serving as a meeting ground for sharing scientific developments and discoveries, the meeting also serves as a locus for mentoring and career development involving younger scientists. The meeting will be chaired by Prof. David Beratan of Duke University, and he will be assisted by other faculty from the region: Profs. Weitao Yang (Duke), Patrick Charbonneau (Duke), Yosuke Kanai (University of North Carolina - Chapel Hill), Zhiyue Lu (University of North Carolina - Chapel Hill), and Elena Jakubikova (North Carolina State University). This group will form a conference commitee that will define thematic topics for the conference, will invite speakers, and will assist with running the conference.

14 SOLAR ENERGY↗
NASA NTRS1996

Theoretical Chemistry At NASA Ames Research Center

The theoretical work being carried out in the Computational Chemistry Branch at NASA Ames will be overviewed. This overview will be followed by a more in-depth discussion of our theoretical work to determine molecular opacities for the TiO and water molecules and a discussion of our density function theory (DFT) calculations to determine the harmonic frequencies and intensities to the vibrational bands of polycyclic aromatic hydrocarbons (PAHs) to assess their role as carriers to the unidentified infrared (UIR) bands. Finally, a more in-depth discussion of our work in the area of computational molecular nanotechnology will be presented.

Langhoff, Stephen↗
NASA NTRS1987

Theoretical approaches to metal chemistry

Theoretical calculations on metals ranging from very accurate ab initio studies of diatomic and triatomic systems to model studies of larger clusters are presented. Recent improvements in the representation of one-particle and n-particle spaces have made possible the prediction that Al2 has a 3Pi(u) ground state, even though the 3Sigma(-)g state lies within 200/cm. Results suggest that cluster geometry varies dramatically with cluster size, and that rather large clusters are required before the bulk structure becomes optimal. Al cluster studies show that three-body terms are needed for quantitative agreement with ab initio calculations.

Bauschlicher, Charles W.↗
DOE OSTI2022

libwfa: Wavefunction analysis tools for excited and open‐shell electronic states

Abstract An open‐source software library for wavefunction analysis, libwfa, provides a comprehensive and flexible toolbox for post‐processing excited‐state calculations, featuring a hierarchy of interconnected visual and quantitative analysis methods. These tools afford compact graphical representations of various excited‐state processes, provide detailed insight into electronic structure, and are suitable for automated processing of large data sets. The analysis is based on reduced quantities, such as state and transition density matrices (DMs), and allows one to distill simple molecular orbital pictures of physical phenomena from intricate correlated wavefunctions. The implemented descriptors provide a rigorous link between many‐body wavefunctions and intuitive physical and chemical models, for example, exciton binding, double excitations, orbital relaxation, and polyradical character. A broad range of quantum‐chemical methods is interfaced with libwfa via a uniform interface layer in the form of DMs. This contribution reviews the structure of libwfa and highlights its capabilities by several representative use cases. This article is categorized under: Software > Quantum Chemistry Theoretical and Physical Chemistry > Spectroscopy

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Combustion chemistry in the twenty-first century: Developing theory-informed chemical kinetics models

Over the past 20 to 25 years theoretical chemistry (particularly theoretical chemical kinetics) has played an increasingly important role in developing chemical kinetics models for combustion. Theoretical methods of obtaining rate parameters are now competitive in accuracy with experiment, particularly for small molecules. Moreover, theoretical methods can deal with conditions that experiments frequently cannot. In addition to increased accuracy, theory has rejuvenated methods and discovered phenomena that were completely unappreciated, or at least underappreciated, in the 20th century. Our primary interest here is in molecular-level issues, i.e. in calculating rate and transport parameters. However, dealing with kinetics models that involve thousands of reactions and hundreds of species is important for practical applications and is relatively new to the 21st century. Theory, in a general sense, and theoretical methods development have a role to play here too. We discuss in this review all these topics in some detail with an emphasis on issues and methods that have emerged in the last 20 years or so. Even so, our review is selective, rather than comprehensive, out of necessity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Low-Lying Excited States of Linear All- Trans Polyenes: Insights from Analytic Gradient and Nonadiabatic Coupling Calculations Based on Multireference Configuration Interaction

Polyenes serve as a rigorous test for theoretical models and electronic structure methods, playing a key role in advancing computational and theoretical chemistry. Here, we present a high-level theoretical investigation of linear, all-trans polyenes using energy gradients and nonadiabatic coupling vectors based on an MR-CISD wave function to describe electronic transitions involving the ground state (1 1 A g – ) and three low-lying excited states (2 1 A g – , 1 1 B u + , and 2 1 B u – ) of hexatriene, octatetraene, and decapentaene. This approach enables accurate evaluation of both adiabatic and vertical excitation and emission energies, yielding results in excellent agreement with experiment, as well as locating minima on the crossing seam between adiabatic states. Our results show that vertical excitation energies to the 1 1 B u + state are blue-shifted by 0.2–0.3 eV relative to the experimental absorption maximum, whereas the vertical emission energy from the 2 1 A g – state is red-shifted by ∼0.2 eV relative to the experimental emission maximum. Upon relaxation from the Franck–Condon geometry, the 2 1 A g – state stabilizes by around 1 eV, compared to 0.2–0.3 eV for the 1 1 B u + state. An analysis of the S 1 /S 0 crossing seam in hexatriene shows that its minimum involves asymmetric backbone deformations and provides an efficient channel for ultrafast internal conversion to the ground state, consistent with the absence of detectable fluorescence in this molecule. These results demonstrate the power of analytic gradients and nonadiabatic coupling vectors based on an MR-CISD wave function for accurately characterizing the electronic structure and photophysics of polyenes.

Excited states↗
DOE OSTI2023

Tribute to José N. Onuchic

This Festschrift Virtual Special Issue in The Journal of Physical Chemistry B is dedicated to the scientific contributions of Prof. José Nelson Onuchic. It serves as a celebration of his years of service, mentorship, and leadership to the biological physics, theoretical chemistry, and computational biology communities. This collection of more than 60 articles has been compiled from an extensive network of scientists that have, in distinct ways, been impacted by the scientific legacy of Prof. Onuchic. It is a written testament to how his work has influenced many areas related to the physics and chemistry of biological systems. In conclusion, this Festschrift provides a good sample of the areas in that Professor Onuchic has had a direct impact via collaboration, mentorship, and scientific dissemination of his research.

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS2011

On the Formation of Interstellar Water Ice: Constraints from a Search for Hydrogen Peroxide Ice in Molecular Clouds

Recent surface chemistry experiments have shown that the hydrogenation of molecular oxygen on interstellar dust grains is a plausible formation mechanism, via hydrogen peroxide (H2O2), for the production of water (H2O) ice mantles in the dense interstellar medium. Theoretical chemistry models also predict the formation of a significant abundance of H2O2 ice in grain mantles by this route. At their upper limits, the predicted and experimental abundances are sufficiently high that H2O2 should be detectable in molecular cloud ice spectra. To investigate this further, laboratory spectra have been obtained for H2O2/H2O ice films between 2.5 and 200 micron, from 10 to 180 K, containing 3%, 30%, and 97% H2O2 ice. Integrated absorbances for all the absorption features in low-temperature H2O2 ice have been derived from these spectra. For identifying H2O2 ice, the key results are the presence of unique features near 3.5, 7.0, and 11.3 micron. Comparing the laboratory spectra with the spectra of a group of 24 protostars and field stars, all of which have strong H2O ice absorption bands, no absorption features are found that can definitely be identified with H2O2 ice. In the absence of definite H2O2 features, the H2O2 abundance is constrained by its possible contribution to the weak absorption feature near 3.47 micron found on the long-wavelength wing of the 3 micron H2O ice band. This gives an average upper limit for H2O2, as a percentage of H2O, of 9% +/- 4%. This is a strong constraint on parameters for surface chemistry experiments and dense cloud chemistry models.

Smith, R. G.↗
DOE OSTI2025

Bayesian optimization of entropy-stabilized metal fluoride conversion cathodes and their synthesis

Fluoride-based conversion cathodes are promising for next-generation Li ion batteries because of their high voltage and energy densities. High entropy earth abundant fluoride cathodes are attractive for sustainable battery because of the potentially higher cycling stability. While Ni and Co containing equimolar alloys stabilized by high entropy were considered previously, Ni and Co free non-equimolar metal alloy compositions might offer new opportunities to increase materials stability and average voltage. This opportunity was pursued using Bayesian optimization of average voltage for the computational prediction of (Fe x1 Cu x2 Zn x3 Mn x4 Mg x5 )F 2 cathode chemistries. Theoretical voltage, room temperature free energy, and electronic structure of potentially high voltage compositions were computed using density functional theory calculations. Here, the experimental realization of non-equimolar quinary Co and Ni free fluorides with stable rutile single phase and improved conversion reaction voltage by up to 28 % compared to the equimolar alloy demonstrated the power of Bayesian optimization methods for the computationally guided experimental synthesis of fluoride cathodes. Finally, non-equimolar cathode chemistries were found with cycling stability superior to known multi-element fluorides.

25 ENERGY STORAGE↗
DOE OSTI2021

InteraChem: Virtual Reality Visualizer for Reactive Interactive Molecular Dynamics

Interactive molecular dynamics in virtual reality (IMD-VR) simulations provide a digital molecular playground for students as an alternative or complement to traditional molecular modeling kits or 2D illustrations. Previous IMD-VR studies have used molecular mechanics to enable simulations of macromolecules such as proteins and nanostructures for the classroom setting with considerable success. Here, we present the InteraChem molecular visualizer, intended for reactive IMD-VR simulation using semiempirical and ab initio methods. InteraChem visualizes not only the molecular geometry but also (1) isosurfaces such as molecular orbitals and electrostatic potentials and (2) two-dimensional graphs of time-varying simulation quantities such as kinetic/potential energy, internal coordinates, and user-applied force. Additionally, InteraChem employs speech recognition to facilitate user interaction and introduces a novel “atom happiness” visualization using emojis to indicate the energetic feasibility of a particular bonding arrangement. Furthermore, we include a set of accompanying exercises that we have used to teach chemical reactivity in small molecular systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Tunable ferroelectricity in oxygen-deficient perovskites with Grenier structure

Using first-principles calculations, we predict that tunable ferroelectricity can be realized in oxide perovskites with the Grenier structure and ordered oxygen vacancies. Specifically, we show that R 1/3 A 2/3 FeO 2.67 solids (where R is a rare-earth ion and A an alkaline-earth cation) exhibit polar phases, with a spontaneous polarization tunable by an appropriate choice of R and A. We find that larger cations combined with small R elements lead to a maximum in the polarization and to a minimum in the energy barriers required to switch the sign of the polarization. Ferroelectricity arises from cooperative distortions of octahedral and tetrahedral units, where a combination of rotational and sliding modes controls the emergence of polarization within three-dimensional connected layers. Our results indicate that polar Grenier phases of oxide perovskites are promising materials for microelectronic applications and, in general, for the study of phenomena emerging from breaking inversion symmetry in solids.

Electronic devices↗