I am interested in photochemical processes occurring in the atmosphere. Many pollutants from anthropogenic and industrial sources are emitted to the atmosphere, affecting the equilibrium of its constituents and damaging our environment. It is therefore of great significance to fully understand the photochemical reactions following irradiation of important components. Our focus in the recent years is mainly on the photochemistry of carbonyl containing groups, such as pentanal, pinonic acid and cyclohexanone. Cluster effects (i.e. a cluster of five pentanal molecules) have been studied as well, to our knowledge for the first time.
The theoretical approach in these studies is applying molecular dynamics simulations using a semiempirical potential for the excited state, enabling long-time simulations as well as the study of large molecules and even clusters. These simulations provide us with the reaction pathways, their yields, mechanisms and timescales after photochemical excitation of the molecule (and clusters) under study.
(a) Structure Prediction of Biomolecules, using DEEPSAM as structure prediction tool (see references, below). This work has been done at Benny Gerber's group. Only recently, I am using DEEPSAM in a research project done at the Jerusalem College of Technology (JCT).
(b) A Parallel Programming Methodology based on what we call Flexible Computation (see references, below). This work has been done at the FlexComp Lab of JCT.
Dr. McCaslin began her research career spring 2011 at Lawrence Berkeley National Laboratory crystalizing proteins relevant to the study of Photosystem II. However, once she dabbled in theoretical research, she was an instant convert. Dr. McCaslin performed research with Prof. Martin Head-Gordon during her final year of her undergraduate degree, studying small sulfate-water clusters. After completing a BS in Chemical Biology in the spring of 2012 she answered the call of Texas and began graduate school at UT Austin in the fall of 2012 with Prof. John Stanton. Dr. McCaslin explored a wide variety of research projects during graduate school, including constructing and benchmarking novel atomic natural orbital-type basis sets for use in spin-free exact two-component relativistic calculations, designing and building a module to analytically transform full quartic force fields and vibrational/rotational parameters between isotopomers, and performing vibrational and rotational calculations in collaboration with experimental chemists to assign spectra and calculate best-fit structures. Dr. McCaslin completed her PhD in the Fall of 2016. Because moving to Texas from California wasn’t enough of a culture shock, Dr. McCaslin accepted a position at the Hebrew University of Jerusalem with Prof. Benny Gerber as a Zuckerman STEM Leadership Postdoctoral Fellow in January 2017.
I am currently performing quantum chemical calculations to have structural information of N2O5+(H2O)n clusters. Furthermore, ab initio molecular dynamics are used in order to study the N2O5 hydrolysis reaction for nano-size clusters. Besides, the reactive uptake of N2O5 on salty water is studied by means of molecular dynamics simulations.
I am interested in vibrational spectroscopy analysis of biological molecules. In my Ph.D. the main study was on the vibrational spectroscopy of C-H stretches in organic molecules, such as hydrocarbons. These stretches are strongly anharmonic, and thus methods including anharmonicity have to be used. [1]
Anharmonic calculations using the Vibrational Self-Consistent Field (VSCF) method were carried out, and compared with IR experiments in liquid phase and with IR experiments in a Ne matrix. [2]
Another study introduced an improved hybrid MP2/MP4 ab initio potential for vibrational spectroscopy calculations which is very accurate, yet without high computational demands. [3]
For my M.Sc. I studied polynitrogen molecules, which are composed entirely out of nitrogen atoms. I find these molecules really interesting because of their unusual bonding. Our main result was the prediction of a new phase of solid nitrogen composed out of N8 molecules. For our publication on N8, click here.
For my Ph.D. I now focus on two main research directions:
1. Using molecular dynamics to study atmospherically-relevant chemical reactions. For our recent publication on the formation of carbonic acid on ice particles, click here.
2. Developing a method to perform quantum molecular dynamics for large molecules using ab initio potentials. For our recent paper in JCTC, click here.
1) The gas phase reaction dynamics of sugars and protons with and without water, using a molecular dynamics approach.
2) Providing computational details for the interpretation of experimental gas phase vibrational spectra of sugars, in various states of ionization and hydration, with complementary usage of the vibrational self-consistent field (VSCF) method and DFT-D molecular dynamics.
This study seeks to identify the critical structural motifs of sugar conformers that determine the yield and selectivity of the hydrolysis of sugars in the gas phase.
I study cooperative effects of ionization in systems of multiple acid and base molecules. We have lately found out that system’s symmetry leads to concerted ionization events in small symmetric clusters of water and HX molecules. Furthermore, I am interested in the computation of chemical processes of atmospheric relevance. This includes mainly proton transfers in atmospheric clusters, using quantum mechanical methods as well as classical methods.
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