A5036375875- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Nuclear physics research studies
- Nuclear Physics and Applications
- High-Energy Particle Collisions Research
- Atomic and Molecular Physics
- DNA and Nucleic Acid Chemistry
- Advanced NMR Techniques and Applications
- X-ray Diffraction in Crystallography
- Ionic liquids properties and applications
- Photochemistry and Electron Transfer Studies
- Machine Learning in Materials Science
- Synthesis and Properties of Aromatic Compounds
- Acoustic Wave Resonator Technologies
- Catalytic Processes in Materials Science
- Quantum Chromodynamics and Particle Interactions
- Crystallography and molecular interactions
- Crystallization and Solubility Studies
- Inorganic Fluorides and Related Compounds
- Luminescence and Fluorescent Materials
- Catalysis and Oxidation Reactions
- Electrocatalysts for Energy Conversion
- Astronomical and nuclear sciences
- Synthesis and properties of polymers
- Solid-state spectroscopy and crystallography
University of Pittsburgh
2013-2021
Florida Gulf Coast University
2020-2021
Clinical Physiology Associates
2021
Pittsburgh Quantum Institute
2015-2019
University of California, Berkeley
2010-2015
Q Chem (United States)
2014
Ludwig-Maximilians-Universität München
2012-2013
Lawrence Berkeley National Laboratory
2011
University of Tübingen
2005-2009
Heinrich Heine University Düsseldorf
2008
Molecular force fields have been approaching a generational transition over the past several years, moving away from well-established and well-tuned, but intrinsically limited, fixed point charge models toward more intricate expensive polarizable that should allow accurate description of molecular properties. The recently introduced AMOEBA field is leading publicly available example this next generation theoretical model, to date, it has only received relatively limited validation, which we...
The current understanding of ligand effects in transition metal catalysis is mostly based on the analysis catalyst–substrate through-bond and through-space interactions, with latter commonly considered to be repulsive nature. dispersion interaction between substrate, a ubiquitous type attractive noncovalent interaction, seldom accounted for context transition-metal-catalyzed transformations. Herein we report computational model quantitatively analyze different types interactions reactivity....
A Laplace-transformed second-order Møller–Plesset perturbation theory (MP2) method is presented, which allows to achieve linear scaling of the computational effort with molecular size for electronically local structures. Also systems a delocalized electronic structure, cubic or even quadratic behavior achieved. Numerically significant contributions atomic orbital (AO)-MP2 energy are preselected using so-called multipole-based integral estimates (MBIE) introduced earlier by us [J. Chem. Phys....
We derive rigorous multipole-based integral estimates (MBIE) in order to account for the distance dependence occurring atomic-orbital (AO) formulations of electron correlation theory, where our focus is on AO-MP2 theory within a Laplace scheme. find exact transformed products an extremely early onset linear-scaling behavior and very small number significant products. To preselect we adapt MBIE method as upper bound. In this way it possible exploit favorable scaling observed reduce estimated...
The CO2ν3 asymmetric stretching mode is established as a vibrational chromophore for ultrafast two-dimensional infrared (2D-IR) spectroscopic studies of local structure and dynamics in ionic liquids, which are interest carbon capture applications. CO2 dissolved series 1-butyl-3-methylimidazolium-based liquids ([C4C1im][X], where [X](-) the anion from hexafluorophosphate (PF6 (-)), tetrafluoroborate (BF4 bis-(trifluoromethyl)sulfonylimide (Tf2N(-)), triflate (TfO(-)), trifluoroacetate...
The performance of 24 density functionals, Hartree-Fock, and MP2 is assessed with respect to the CCSD(T)/CBS* energetics 49 sulfate-water clusters three six water molecules. Included among functionals are GGA, meta-GGA, hybrid double as well LDA. Three types dispersion corrections (VV10, XDM, -D) tested in conjunction these functionals. 26 methods compared using relative binding energies main criteria. It was discovered that a majority unable simultaneously capture physics necessary describe...
Efficient estimates for the preselection of two-electron integrals in atomic-orbital based Møller-Plesset perturbation theory (AO-MP2) are presented, which allow evaluating AO-MP2 energy with computational effort that scales linear molecular size systems a significant HOMO-LUMO gap. The on our recently introduced QQR approach [S. A. Maurer, D. S. Lambrecht, Flaig, and C. Ochsenfeld, J. Chem. Phys. 136, 144107 (2012)10.1063/1.3693908], exploits asympotic decay integral values increasing...
Reactions of the halo systems 11Be and 11Li (at 460 280 MeV/nucleon) with a carbon target demonstrate that ( n+9Li) has an (unbound) l=0 ground state very close to threshold. The neutron appreciable (1s1/2)2 (0p1/2)2 components.Received 20 December 1994DOI:https://doi.org/10.1103/PhysRevLett.75.1719©1995 American Physical Society
The nuclear response of a medium-mass nucleus ${(}^{136}$Xe) to electromagnetic excitation in near-relativistic heavy-ion collision was investigated the ${\mathrm{reaction}}^{136}$Xe(0.7A GeV)+Pb. From an exclusive measurement neutron decay excited $^{136}\mathrm{Xe}$ projectiles, strong excitations giant resonances and, particular, double isovector dipole resonance were identified. A energy 28.3\ifmmode\pm\else\textpm\fi{}0.7 MeV, width 6.3\ifmmode\pm\else\textpm\fi{}1.6 and total cross...
We present data on collective flow of neutrons in collisons 197Au + at 400 MeV/nucleon. The azimuthal distribution about the beam axis is investigated with respect to reaction plane as determined from light charged particles. ''squeezeout'' neutrons, perpendicular plane, observed for first time. Quantitative agreement a high level accuracy found between behavior and hydrogen ions.Received 29 April 1993DOI:https://doi.org/10.1103/PhysRevLett.71.963©1993 American Physical Society
Within an atomic-orbital-based (AO-based) formulation of second-order Møller–Plesset perturbation theory (MP2), we present a novel screening procedure which allows us to preselect numerically significant two-electron integrals more efficiently, especially for large basis sets. The is based on our recently introduced multipole-based integral estimates (MBIE) method [J. Chem. Phys., 2005, 123, 184102], that exploit the 1/R4 or 1/R6 coupling between electronic charge distributions in...
A new integral estimate for four-center two-electron integrals is introduced that accounts distance information between the bra- and ket-charge distributions describing two electrons. The screening denoted as QQR combines most important features of conventional Schwarz by Häser Ahlrichs published in 1989 [J. Comput. Chem. 10, 104 (1989)] our multipole-based estimates (MBIE) 2005 [D. S. Lambrecht C. Ochsenfeld, J. Phys. 123, 184101 (2005)]. At same time are not only tighter but also much...
Product selectivity of alkane cracking catalysis in the H-MFI zeolite is investigated using both static and dynamic first-principles quantum mechanics/molecular mechanics simulations. These simulations account for electrostatic- shape-selective interactions provide enthalpic barriers that are closely comparable to experiment. Cracking transition states n-pentane lead a metastable intermediate (a local minimum with relatively small escape deeper minima) where proton shared between two...
The absolutely localized molecular orbital (ALMO) model is a fully variational approach which permits polarization of molecules interacting in cluster while prohibiting charge-transfer (or dative interactions) between individual molecules. ALMO can be applied within any density functional theory calculation--the B3LYP employed this work. DFT calculations observables such as optimized geometry, vibrational frequencies and their intensities, vertical detachment energies are performed for the...
The interaction between catalytic nanoparticles (NPs) and their supports, which are often amorphous oxides, has not been well characterized at the atomic level, although it is known that, in some cases, NP–support interactions dominate activity of system. Furthermore, there a lack understanding how support preparation affects both stability NP (resistance to sintering) activity. We present first-principles density functional theory (DFT) calculations on silica supported Pt NPs various sizes....
We derive multipole-based integral estimates (MBIE) as rigorous and tight upper bounds to four-center two-electron integrals in order account for the 1/R distance decay between charge distributions, which is missing Schwarz screening commonly used ab initio methods. Our criteria are valid all angular momenta can be formulated any of multipoles. have found expansion limited dipoles sufficiently estimating Hartree-Fock density-functional theories, while effort negligible. For, e.g., a DNA...
The piezoelectric properties of 2-methyl-4-nitroaniline crystals were explored qualitatively and quantitatively using an electrostatically embedded many-body (EE-MB) expansion scheme for the correlation energies a system monomers within crystal. results demonstrate that hydrogen bonding is inherently interaction, deforming in response to electrostatic environment. We obtain piezo-coefficients excellent agreement with experimental values. This approach reduces computational cost reproduces...
Quantum mechanics/molecular mechanics (QM/MM) models are applied to investigate the adsorption and cracking of n-hexane on ZSM-5 Faujasite zeolite structures. These simulations account for long-range electrostatic midrange van-der-Waals interactions in provide energy barriers that close experimental data. The active acidic site was modeled by dispersion corrected density functional theory (DFT, ω B97X-D6-311/G*). were calculated molecular (MM). adsorbed molecules under investigation...
We present a reinvestigation of sulfate–water clusters SO42– (H2O)n=3–7, which involves several new aspects. Using joint molecular mechanics/first principles approach, we perform exhaustive searches for stable cluster geometries, showing that the landscape is much richer than anticipated previously. check compatibility structures with experiment by comparing vertical detachment energies (VDEs) calculated at B3LYP/6-311++G** level theory and determine energetic ordering isomers...
Organic piezoelectric materials are promising targets in applications such as energy harvesting or mechanical sensors and actuators. In a recent paper (Werling, K. A.; et al. J. Phys. Chem. Lett. 2013, 4, 1365-1370), we have shown that hydrogen bonding gives rise to significant response. this article, aim find organic bonded systems with increased piezo-response by investigating different motifs tailoring the bond strength via functionalization. The largest piezo-coefficient of 23 pm/V is...