Digital Commons Network^™

Il14. Core-Hole Initiated Charge Migration With Tddft, Kenneth Lopata

Southeast Theoretical Chemistry Association Meeting (SETCA)

Attosecond electron dynamics in molecules underpins a range of important processes such as light harvesting, photochemistry, and ultrafast spectroscopy. Modeling these dynamics from first principles is important for predicting and interpreting ultrafast experiments. In the case of large molecules, however, correlated techniques can be prohibitively expensive. Here, time-dependent density functional theory (TDDFT) o↵ers a promising alternative, but limitations in the exchange-correlation functional, especially the adiabatic (local-in-time) approximation limit the accuracy of the results.

In this talk, I will present a study demonstrating the validity of TDDFT for core-hole triggered charge migration in nitrosobenzene. Specifically, by initializing the system with an …

Il13. Proton-Bound Complexes: A Major Challenge For Vibrational Analysis, Joel Bowman

Southeast Theoretical Chemistry Association Meeting (SETCA)

I will review a general approach to develop and employ full-dimensional potential and dipole moment surfaces in VSCF/VCI calculations of highly-coupled vibrational motion in proton-bound complexes. Examples include the proton-bound N₂ [1] and CO[2] dimers and proton-bound water clusters, H₇O₄⁺ and H₉O₄⁺.[3] A controversy about the latter “Eigen” complex will be addressed, as it points out some limitations of “ab initio molecular dynamics” approaches to IR spectroscopy.

Cl8. Can We Find Interstellar Nitrogen In Exotic Molecules?, Ryan C. Fortenberry

Southeast Theoretical Chemistry Association Meeting (SETCA)

The nitrogen molecule is one of the most strongly bound systems known. It also makes up a vast majority of the Earth’s atmosphere. However, the origin of this molecule in the atmosphere is still largely unknown. Is the nitrogen primordial to the Earth or was it formed through biological or geological processes? One way to find out is through observation of stellar systems similar to the early solar system. The chief issue is that N₂ is not observable through vibrational or rotational means due to a lack of a permanent or induced dipole moment, and electronic observation is difficult …

Cl7. Resonance Energies And Lifetimes From Extrapolation Methods: Robust Algorithms And A Critical Analysis, Thomas Sommerfeld

Southeast Theoretical Chemistry Association Meeting (SETCA)

An electronic resonance is an electronic state of an (N + 1)-electron system that lies energetically above the N-electron system, and therefore in the scattering continuum of the N-electron state. Examples are temporary anions such as N-₂, the Be−, or the benzene anion, small dianions in the gas phase such as CO²⁻ ₃ or SO²⁻ ₄, core-ionized atoms and molecules decaying via the Auger process, and the Auger-like decay of inner-valence ionized clusters. Resonances are characterized by their so-called resonance position, E_r, that is, the energy above the N-electron state, and …

Il12. Density Functional Theory Method For Nondynamic/Strong Correlation, Jing Kong

Southeast Theoretical Chemistry Association Meeting (SETCA)

Nondynamic and strong correlation imposes the major challenge to the current density functional theory (DFT), and counts for the majority of the failures of DFT in a variety of areas such as catalysis, organic open-shell molecules and materials. The problem is often characterized as multireference in nature. In this talk, we will present a density functional model based on single-determinant Kohn-Sham density functional theory [1]. It combines Becke’13 method with a new model for kinetic correlation via adiabatic connection based on physical arguments and some exact conditions for both the weak and strong correlations. The result is a single-term functional …

Il11. A Direct Measure Of Metal-Ligand Bonding Replacing The Tolman Electronic Parameter, Elfi Kraka

Southeast Theoretical Chemistry Association Meeting (SETCA)

The prediction of the catalytic activity of transition metal complexes is a prerequisite for homogeneous catalysis. The Tolman Electronic Parameter (TEP) was derived to provide this information. It is based on the CO stretching frequencies of metal-tricarbonyl complexes LM(CO)3 with varying ligands L. It has been used in hundreds of cases as is documented by as many publications.

We show [1] that the TEP is misleading as i) it is not based on mode-decoupled CO stretching frequencies and ii) a quantitatively correct or at least qualitatively reasonable relationship between the TEP and the metal-ligand bond strength does not exist. This …

Cl6. Folding Mechanisms Of Small Proteins Gb1 And Lb1, Qianyi Cheng

Southeast Theoretical Chemistry Association Meeting (SETCA)

The B1 domains of protein G (GB1) and protein L (LB1) are two small proteins that bind to antibody immunoglobulin G (IgG). GB1 and LB1 are similar in size (about 60 residues), and also have an overall similar structure (β-hairpin--α-helix--β-hairpin). However their sequences are very different, possessing only 15% identity in a structure-based alignment [1,2]. Therefore, there are interesting comparisons in their folding mechanisms. Experimental evidence indicates that LB1 folds in a two-state manner; while GB1 folds in a more complex way -- an early stage intermediate may exist in the folding path. The folding mechanisms are still under extensive …

Cl5. Excited State Transition Energies And Properties In Solution From A Smooth Dielectric Model, J. Coleman Howard

Southeast Theoretical Chemistry Association Meeting (SETCA)

A quantum mechanical solvation model is presented for a solute embedded in a polarizable dielectric medium, where the solute cavity is determined from an electronic isodensity surface in a smooth two-parameter model previously implemented in plane-wave-based density functional theory computations. In this work, solvent-solute interactions are incorporated into a Hartree-Fock framework and captured via numerical solution of the nonhomogenous Poisson equation on a real-space grid through an interface between PSI4 and the DL_MG multigrid solver library. The method is applied here to compute excited state transition energies and properties with the equation-of-motion coupled-cluster singles and doubles method (EOM-CCSD). Results are …

Il10. An Economical Theory For Chemical Bonding, Evangelos Miliordos

Southeast Theoretical Chemistry Association Meeting (SETCA)

The last hundred years chemists have come up with several effects to explain the chemical bonding. A list of the most common ones include hydridization, hypervalency, hyperconjugation, aromaticity, resonance, electronegativity, and different kinds of orbitals such as bonding, anti-bonding, non-bonding, HOMO, LUMO, SOMO, etc. Each of these theories is appropriately designed to describe a specific group of molecular systems, and may cause confusion or rise contradictions when applied to different systems. The ongoing discovery of "exotic" species urges an economic and clear theory which can explain the bonding in terms of the electrostatic forces and spin coupling. We presently show …

Poster Session, Nathan J. Deyonker

Southeast Theoretical Chemistry Association Meeting (SETCA)

Posters presented by:

• P01: Adam S. Abbott, University of Georgia
• P02: Yasmeen Abdo, University of Mississippi
• P03: Vibin Abraham, Virginia Tech
• P04: Asim Alenaizan, Georgia Institute of Technology
• P05: Isuru R. Ariyanthna, Auburn University
• P06: Brandon W. Bakr, Georgia Institute of Technology
• P07: [Matthew Bassett, Georgia Southern University]
• P08: Alexandre P. Bazanté, University of Florida
• P09: Andrea N. Becker, University of Tennessee
• P10: Randi Beil, University of Tennessee
• P11: Andrea N. Bootsma, University of Georgia/Texas A&M University
• P12: Adam Bruner, Louisiana State University
• P13: Lori A. Burns, Georgia Institute of Technology
• P14: Chanxi Cai, Emory University
• P15: Katherine A. Charbonnet, …

Il9. Thermochemistry: Not As Boring As You Might Think, John F. Stanton

Southeast Theoretical Chemistry Association Meeting (SETCA)

Developed during the last decade by Ruscic and collaborators at Argonne National Laboratory, Active Thermochemical Tables (ATcT) represents an entirely new and revolutionary way to approach the subject of thermochemistry. Traditional thermochemistry has advanced piecemeal and willy nilly, through individual spectroscopic, kinetic, calorimetric, etc. mea-surements often supplemented by 'recommendation of 'standard (in the non-thermodynamic sense) through the actions of various critical review committees (NIST-JANAF, CODATA, etc.). In contrast, ATcT is a holistic approach that views each molecule as connected in principle to all other species through within constructs called thermochemical networks. In ATcT, thermochemical parameters such as bond energies, ionization …

Il8. Why Computational Chemists Should Not Be Ignored: The Effect Of Ether And Amine Bridges In The Conjugation Of Monomacrocyclic Dendrimers, Shelley A. Smith

Southeast Theoretical Chemistry Association Meeting (SETCA)

Conjugated dendrimers have been studied for their use in preparing photoreactive materials and for their light harvesting properties. One of the goals of an experimental research group at my institution is to design and prepare flat, two-dimensional dendrimers. It has been found that when twisting occurs about the single bonds of the dendrons, there is a decrease in energy transfer and therefore loss of conjugation and reduced light harvesting properties. The experimental group has been synthesizing "flat" dendrimers that they think cannot lose this conjugation due to the ethynyl units being locked in place by ether connections. These ether connections …

Cl4. Cam-Lda0: The Reincarnation Of The Local Density Approximation, Carlos H. Borca

Southeast Theoretical Chemistry Association Meeting (SETCA)

Kohn-Sham Density Functional Theory (KS-DFT) is the most popular electronic structure method applied throughout science and engineering. The exchange-correlation (XC) local density approximation (LDA) was the earliest density functional used to investi-gate the electronic structure of chemical systems in KS-DFT. Since then, the LDA has been the bedrock of the field of density functional development. In this contribution, we discuss the roles of the non-local exchange and the local-density approximation in the improvement of the quality of the fundamental gap, and in the enhancement excitation-energy estimations. We suggest that the combination of these two concepts is dominant for the calculation …

Il7. Theoretical Studies Of Phosphoryl Transfer Enzymes, Charles Edwin Webster

Southeast Theoretical Chemistry Association Meeting (SETCA)

The mechanisms of phosphoryl transfer enzymes have garnered considerable attention. Fluoro-containing metal species have been used as transition-state and ground-state analogues in a variety of phosphoryl transfer enzymes and have shed light on the nature of the requirements in the active site to catalyze phosphoryl transfer. Some of our work on phospholipase D (PLD), tyrosyl-DNA phosphodiesterase I (Tdp1), human histidine triad nucleotide binding protein 1 (hHINT1), fructose-1,6-bisphosphatase (FBP), cyclic adenosine monophosphate dependent protein kinase (cAPK), and β-phosphoglucomutase (β-PGM) will be discussed.

• Charles Edwin Webster, Mississippi State University
• Guangchao Liang, Mississippi State University
• Robert W. Lamb, Mississippi State University
• Katherine N. …

Il6. Two-Step Model Of Ultrafast Interfacial Electron Transfer In Dye-Semiconductor Assemblies, Elena Jakubikova

Southeast Theoretical Chemistry Association Meeting (SETCA)

Interfacial electron transfer (IET) is one of the steps in light-harvesting process that occurs in various assemblies for solar energy conversion, such as dye-sensitized solar cells or dye-sensitized photoelectrosynthesis cells. This work investigates IET in a model pyridine-TiO₂ assembly, with the goals to assess the validity of the Fermi's golden rule for calculation of the IET rates, understand the importance of conformational sampling in modeling the IET process, and establish an approach to rapid computational screening of dye-sensitizers that undergo fast IET into the semiconductor. Our results suggest that IET is a two-step process, in which the electron is …

Cl3. Interaction Of Atomic Oxygen With Ag(111) And Ag(110) Surfaces: Oxygen Adsorption And Kinetics At Surface Versus Subsurface, Sara Isbill

Southeast Theoretical Chemistry Association Meeting (SETCA)

Transition metals are commonly used to catalyze transformations of small or-ganic compounds, but the mechanisms of these catalytic reactions are not yet completely understood. Silver surfaces are important industrial catalysts for the partial oxidation of ethylene to ethylene oxide and methane to methanol. While significant strides have been taken towards revealing the complex chemical pathways of oxidation reactions on silver sur-faces, the role of subsurface oxygen (oxygen adsorbed just beneath the surface) in surface reconstruction and oxidative catalysis by silver has yet to be elucidated. Does subsurface oxygen affect catalysis by changing the electronic and geometric properties of silver, or …

Il5. Interactions Of Co₂ With Metal Organic Frameworks And Metal Oxide Nanoclusters, David A. Dixon

Southeast Theoretical Chemistry Association Meeting (SETCA)

Acid gases, especially CO₂, play an important role in a range of large-scale energy applications. Acid gas conversion can make use of reactive sorbents and catalysts, but these materials must not substantially degrade under operating conditions. Metal oxides, metal organic frameworks, and clays may be used for these purposes, but interactions of acid gases with these complex materials are poorly understood. In order to improve our understanding of such materials, we have been using electronic structure methods to better understand these interactions in terms of ‘physisorption’ and ‘chemisorption’ type processes. The interactions of CO₂ with models of …

Il4. The Molecular Science Software Institute, T. Daniel Crawford

Southeast Theoretical Chemistry Association Meeting (SETCA)

The Molecular Sciences Software Institute (MolSSI) is a nexus for science, education, and cooperation serving the worldwide community of computational molecular scientists — a broad field including of biomolecular simulation, quantum chemistry, and materials science. The Institute, which was recently funded by the National Science Foundation as part of the White House’s National Strategic Computing Initiative, will spur significant ad-vances in software infrastructure, education, standards, and best-practices that are needed to enable the molecular science community to open new windows on the next generation of scientific Grand Challenges, ranging from the simulation of intrinsically disordered proteins associated with a range …

Cl2. Psi4numpy: An Interactive Quantum Chemistry Programming Environment For Reference Implementation, Rapid Development, And Education, Dominic A. Sirianni

Southeast Theoretical Chemistry Association Meeting (SETCA)

A cornerstone of the development of novel quantum chemistry methods is the translation of paper-and-pencil theory into an efficient computer program. To do this, low-level programming languages are typically employed; however, such implementations tend to be convoluted, as raw speed is the focus rather than either readability or reproducibil-ity. Any attempt at re-implementation must then proceed with the originally published equations as the only reference, whereby critical programming details must be re-discovered through a similarly heroic effort to the original implementation. To address these issues, the Psi4NumPy project [1] leverages the Psi4 quantum chemistry package and the Nu-merical Python (NumPy)library …

Il3. Electron Correlation Methods For Near-Degenerate Electronic States Based On The Driven Similarity Renormalization Group, Francesco A. Evangelista

Southeast Theoretical Chemistry Association Meeting (SETCA)

We have recently demonstrated that it is possible to combine conventional Quantum Chemistry many-body approaches with flow renormalization group methods to produce a new family of electronic structure theories. These methods have several advantages: (i) they are numerically-robust and avoid intruder states, (ii) they lead to equation that are relatively simple, and (iii) they are easily generalized to multi-determinantal reference states. An important aspect of our work has been to reformulate the similarity renormalization group (SRG) of Głazek and Wilson and Wegner [1,2] into a practical quantum chemistry approach, the driven SRG (DSRG) [3]. Recently, we examined new approximation schemes …

Il2. Tools For The Computational Design Of Asymmetric Catalysts, Steven E. Wheeler

Southeast Theoretical Chemistry Association Meeting (SETCA)

The development of new catalysts for asymmetric organic reactions typically proceeds by the experimental screening of potential new designs. This requires the synthesis and testing of many catalysts that will ultimately prove ineffective. We envision an alternative approach to catalyst development driven by the computational screening of virtual libraries of potential designs. Toward this end, I will describe a Perl module (AaronTools) that provides functions for building, manipulating, and analyzing molecular and supramolecular structures, creating input files and parsing output files from popular electronic structure packages, and interacting with common batch queuing systems. I will also introduce a computational toolkit …

Cl1. New Primitive Gaussians Based On Per Electron Energy Convergence Criteria, Daniel Claudino

Southeast Theoretical Chemistry Association Meeting (SETCA)

Even the simplest electronic structure calculation depend on the proper choice of two parameters, namely level of theory and basis set, and they can be equally important in obtaining meaningful and accurate answers. Notwithstanding the central role of correlation energy in high-accuracy calculations, Pople-style[1] and correlation consistent,[2] arguably the most popular basis sets, are based on theories with well-known deficiencies in the de-scription of the correlation phenomenon. The former is optimized at the SCF level, that is, it does not come from a correlated method, while the latter depends on truncated config-uration interaction (CISD) calculations, a non-size extensive method. On …

Il1. Quantum Chemistry Without Wavefunctions, A. Eugene Deprince Iii

Southeast Theoretical Chemistry Association Meeting (SETCA)

Complete active space self-consistent field (CASSCF) methods are enormously important in quantum chemistry, as they allow for the description of states dominated by more than one electronic configuration. In CASSCF, the electronic structure of the active space is often represented by a configuration interaction (CI) expansion of the active-space wave function. Unfortunately, the exponential complexity of the full CI wave function severely limits the size of the active space that can practically be considered. For a large-active-space CASSCF algorithm, one must abandon CI in favor of an approach with more desirable scaling properties, such as the density matrix renormalization group …

Registration (Light Snacks), Conference Attendees

Southeast Theoretical Chemistry Association Meeting (SETCA)

No abstract provided.