A5027561105- Spectroscopy and Quantum Chemical Studies
- Advanced Chemical Physics Studies
- Photochemistry and Electron Transfer Studies
- Advanced NMR Techniques and Applications
- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Inorganic Fluorides and Related Compounds
- Molecular spectroscopy and chirality
- Insect and Pesticide Research
- Machine Learning in Materials Science
- Advanced X-ray Imaging Techniques
- Free Radicals and Antioxidants
- Molecular Junctions and Nanostructures
- stochastic dynamics and bifurcation
- Protein Structure and Dynamics
- Advanced Electron Microscopy Techniques and Applications
Princeton University
2025
University of Pennsylvania
2021-2023
California University of Pennsylvania
2021-2022
Brown University
2014-2017
John Brown University
2014
Providence College
2014
This article summarizes technical advances contained in the fifth major release of Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library exchange-correlation functionals, along with a suite correlated many-body methods, continues to be hallmark software. The methods include novel variants both coupled-cluster and configuration-interaction approaches based on algebraic diagrammatic construction variational reduced density-matrix methods. Methods...
We describe a gas-phase x-ray scattering experiment capable of capturing molecular motions with atomic spatial resolution and femtosecond time resolution. X-ray free electron lasers can deliver intense pulses ultrashort duration, making them suitable to study ultrafast chemical reaction dynamics in an ultraviolet pump, probe scheme. A cell diffractometer balances sample flow gas density laser focusing conditions provide adequate vector high signal intensity near-uniform excitation...
We aim to observe a chemical reaction in real time using gas-phase X-ray diffraction. In our initial experiment at the Linac Coherent Light Source (LCLS), we investigated model system 1,3-cyclohexadiene (CHD) very low vapor pressures. This serves as benchmark for numerous transformations organic synthesis and natural product biology. Excitation of CHD by an ultraviolet optical pulse initiates electrocyclic that transforms closed ring into open-chain structure 1,3,5-hexatriene. describe...
The accurate description of large molecular systems in complex environments remains an ongoing challenge for the field computational chemistry. This problem is even more pronounced photoinduced processes, as multiple excited electronic states and their corresponding nonadiabatic couplings must be taken into account. Multiscale approaches such hybrid quantum mechanics/molecular mechanics (QM/MM) offer a balanced compromise between accuracy burden. Here, we introduce open-source software...
We revisit the naked transition metal cation (Ti+) and methanol reaction go beyond standard Landau–Zener (LZ) picture when modeling intersystem crossing (ISC) rate between lowest doublet quartet states. use both (i) unconstrained Born–Oppenheimer molecular dynamics (BOMD) calculations with an approximate two-state method to estimate population transfer spin diabats (ii) constrained explore energetically accessible portions of NDOF – 1 seam, where is total number internal degrees freedom....
We implement a rare-event sampling scheme for quantifying the rate of thermally activated nonadiabatic transitions in condensed phase. Our Quantum mechanics/molecular mechanics (QM/MM) methodology uses recently developed Interface NonAdiabatic QM/MM Solvent (INAQS) package to interface an elementary electronic structure and popular open-source molecular dynamics software (GROMACS) simulate electron transfer event between two stationary ions solution acetonitrile solvent molecules....
With the notable exception of some illustrative two-degree-of-freedom models whose surprising classical dynamics has been worked out in detail, theories roaming have largely bypassed issue when and why counterintuitive phenomenon occurs. We propose that a useful way to begin address these issues is look for geodesic (most efficient) pathways through potential surfaces candidate systems. Although manifests itself an unusual behavior at asymptotic geometries, we found case formaldehyde...
We present an efficient set of methods for propagating excited-state dynamics involving a large number configuration interaction singles (CIS) or Tamm-Dancoff approximation (TDA) single-reference excited states. Specifically, (i) following Head-Gordon et al., we implement exact evaluation the overlap singly-excited CIS/TDA electronic states at different nuclear geometries using biorthogonal basis and (ii) employ unified protocol choosing correct phase each adiabat geometry. For many-electron...
Photoinduced processes play a crucial role in multitude of important molecular phenomena. Accurately modeling these an environment other than vacuum requires detailed description the electronic states involved as well how energy flows are coupled to surroundings. Nonadiabatic effects must also be included order describe exchange between and nuclear degrees freedom correctly. In this work, we revisit ring-opening reaction 1,3-cylohexadiene (CHD) solvent environment. Using our newly developed...
We present a new software package called M-Chem that is designed from scratch in C++ and parallelized on shared-memory multi-core architectures to facilitate efficient molecular simulations. Currently, fast dynamics (MD) engine supports the evaluation of energies forces two-body many-body all-atom potentials, reactive force fields, coarse-grained models, combined quantum mechanics (QM/MM) external drivers machine learning, augmented by algorithms are focused gains computational simulation...
We implement a rare-event sampling scheme for quantifying the rate of thermally-activated nonadiabatic transitions in condensed phase. Our QM/MM methodology uses recently developed INAQS package to interface between an elementary electronic structure and popular open-source molecular dynamics software (GROMACS) simulate electron transfer event two stationary ions solution acetonitrile solvent molecules. Nonadiabatic effects are implemented through surface hopping our simulations allow...
The accurate description of large molecular systems in complex environments remains an ongoing challenge for the field computational chemistry. This problem is even more pronounced photo-induced processes, as multiple excited electronic states and their corresponding non-adiabatic couplings must be taken into account. Multiscale approaches such hybrid quantum mechanics/molecular mechanics (QM/MM) offer a balanced compromise between accuracy burden. Here, we introduce open-source software...
We present an efficient set of methods for propagating excited-state dynamics involving a large number electronic states based on configuration interaction singles (CIS) state overlap scheme. Specifically, (i) following Head-Gordon et al, we implement exact evaluation the singly-excited at different nuclear geometries using biorthogonal basis, and (ii) employ unified protocol choosing correct phase each adiabat geometry. For many-electron systems, combination these techniques significantly...
We present an efficient set of methods for propagating excited-state dynamics involving a large number electronic states based on CIS state overlap scheme. Specifically, (i) following Head-Gordon et al, we implement exact evaluation the singly-excited at different nuclear geometries using biorthogonal basis, and (ii) employ unified protocol choosing correct phase each adiabat geometry. For many-electron systems, combination these techniques significantly reduces computational cost...
We report robust initial guesses for the amplitudes and z-vectors in a configuration interaction singles or Tamm–Dancoff approximation calculation that consistently reduce total number of iterations required an excited state often by over 50%. The end result these is practicing chemist can expect to generate optimized structures with wall time reduced as much 30% future without any approximations—simply using information gathered at one geometry applying it another geometry.
The accurate description of large molecular systems in complex environments remains an ongoing challenge for the field computational chemistry. This problem is even more pronounced photo-induced processes, as multiple excited electronic states and their corresponding non-adiabatic couplings must be taken into account. Multiscale approaches such hybrid quantum mechanics/molecular mechanics (QM/MM) offer a balanced compromise between accuracy burden. Here, we introduce open-source software...