A5031214422- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Photochemistry and Electron Transfer Studies
- X-ray Spectroscopy and Fluorescence Analysis
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Molecular Junctions and Nanostructures
- Molecular spectroscopy and chirality
- Crystallography and molecular interactions
- Quantum, superfluid, helium dynamics
- Carbon Nanotubes in Composites
- Protein Structure and Dynamics
- Graphene research and applications
- Electrochemical Analysis and Applications
- Atmospheric Ozone and Climate
- Electron and X-Ray Spectroscopy Techniques
- Mass Spectrometry Techniques and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Inorganic Fluorides and Related Compounds
- Molecular Spectroscopy and Structure
- Catalytic Processes in Materials Science
- Photosynthetic Processes and Mechanisms
- Catalysis and Oxidation Reactions
- Luminescence and Fluorescent Materials
- Fullerene Chemistry and Applications
University of Nottingham
2014-2023
Park University
2014-2020
SLAC National Accelerator Laboratory
2018
Stockholm University
2018
University of Nottingham Ningbo China
2017
Australian National University
2008
Ruhr University Bochum
2006
Rutherford Appleton Laboratory
2002
Scripps Research Institute
1998-2001
Collège de France
2000
Q-Chem 2.0 is a new release of an electronic structure program package, capable performing first principles calculations on the ground and excited states molecules using both density functional theory wave function-based methods. A review technical features contained within presented. This article contains brief descriptive discussions key physical all algorithms theoretical models, together with sample that illustrate their performance. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 1532–1548,
We present a simple algorithm, which we call the maximum overlap method (MOM), for finding excited-state solutions to self-consistent field (SCF) equations. Instead of using aufbau principle, algorithm maximizes between occupied orbitals on successive SCF iterations. This prevents variational collapse ground state and guides process toward nearest, rather than lowest energy, solution. The resulting can be treated in same way as ground-state solution and, particular, derivatives energies...
The accuracy of core excitation energies and electron binding computed within a Delta self-consistent-field framework is assessed. variational collapse the excited state prevented by maintaining singly occupied orbital using an overlap criterion called maximum method. When applied to wide range small organic molecules, resulting are not systematically underestimated as observed in time-dependent density functional theory agree well with experiment. this approach for states illustrated...
Recent advances in X-ray sources have led to a renaissance spectroscopic techniques the region. These that involve excitation of core electrons can provide an atom specific probe electronic structure and powerful analytical tools are used many fields research. Theoretical calculations often play important role analysis interpretation experimental spectra. In this perspective, we review recent developments quantum chemical absorption spectra, focusing on use time-dependent density functional...
We report calculations of core excitation energies and near-edge X-ray absorption fine structure (NEXAFS) spectra computed with time-dependent density functional theory (TDDFT). TDDFT generalized gradient approximation standard hybrid exchange-correlation functionals is known to underestimate energies. This failure shown be associated the self-interaction error at short interelectronic distances. Short-range corrected are reduce in for first second row nuclei a range molecules level...
ConspectusThe availability of new light sources combined with the realization unique capabilities spectroscopy in X-ray region has driven tremendous advances field spectroscopy. Currently, these techniques are emerging as powerful analytical tools for study a wide range problems encompassing liquids, materials, and biological systems. Time-resolved measurements add further dimension to spectroscopy, opening up potential resolve ultrafast chemical processes at an atomic level. encompasses...
Abstract The availability of X‐ray light sources with increased resolution and intensity has provided a foundation for increasingly sophisticated experimental studies exploiting the spectroscopy core electrons to probe fundamental chemical, physical, biological processes. Quantum chemical calculations can play critical role in analysis these measurements. relatively low computational cost density functional theory (DFT) time‐dependent (TDDFT) make them attractive choices simulating...
Proteins have characteristic circular dichroism spectra in the far-ultraviolet, depending on their secondary structure content. Perhaps most distinctive spectrum is that of α-helical proteins, with an intense positive band centered about 190 nm and a negative, double-peaked minima at 208 220 nm. Traditionally, calculations such from first principles involved parametrizations charge distributions associated electronic states transitions constituent chromophoric groups. The amide group...
A series of substituted benzoyl radicals has been generated by laser flash photolysis alpha-hydroxy ketones, alpha-amino and acyl bis(acyl)phosphine oxides, all which are used commercially as photoinitiators in free radical polymerizations. The have studied fast time-resolved infrared spectroscopy. absolute rate constants for their reaction with n-butylacrylate, thiophenol, bromotrichloromethane oxygen were measured acetonitrile solution. addition to n-butylacrylate range from 1.3 x 10(5)...
The performance of Gaussian basis sets for density functional theory-based calculations core-electron spectroscopies is assessed. convergence binding energies and core-excitation using a range including split-valence, correlation-consistent, polarisation-consistent individual gauge localised orbitals studied. For $$\varDelta $$ self-consistent field first-row elements, relatively small can accurately reproduce the values much larger sets, with IGLO performing particularly well. Calculations...
<italic>meso-t</italic>-Bu-BODIPY produces unusual spectroscopic and photophysical characteristics in comparison to those of related alkylated BODIPY dyes.
The restricted excitation subspace approximation is explored as a basis to reduce the memory storage required in linear response time-dependent density functional theory (TDDFT) calculations within Tamm–Dancoff approximation. It shown that excluding core orbitals and up 70% of virtual construction does not result significant changes computed UV/vis spectra for large molecules. reduced size greatly reduces vectors need be stored when using Davidson procedure determine eigenvalues TDDFT...
The carbon 1s X-ray absorption spectroscopy (XAS) of acetylene, ethylene, and benzene in gas phase adsorbed on the Si(100) surface is studied using time-dependent density functional theory (TDDFT) with hybrid exchange correlation functionals. computed spectra are sensitive to proportion Hartree−Fock exchange-correlation functional. fraction optimized provide accurate predictions → π* excitation energies. In phase, ethylene dominated by excitations further weaker bands at higher energies...
The equation of motion coupled cluster theory including single and double excitations (EOM-CCSD) method is applied to study the X-ray emission spectroscopy water. For 1b1 orbital, a difference about 0.7 eV predicted between tetrahedrally coordinated water molecule in which molecules accepting hydrogen bonds are absent, as proton dissociated from 3a1 orbitals become closer energy. resonantly excited spectrum for 4a1 orbital shows red-shift bands reduction intensity band.
The accuracy of excited states calculated with Kohn-Sham density functional theory using the maximum overlap method has been assessed for calculation adiabatic excitation energies, state structures, and harmonic anharmonic vibrational frequencies open-shell singlet states. computed energies are improved significantly by post self-consistent field spin-purification, but remain too low compared experiment a larger error than time-dependent theory. Excited structures also spin-purification....
The calculation of X-ray emission spectroscopy with equation motion coupled cluster theory (EOM-CCSD), time-dependent density functional (TDDFT), and resolution the identity single excitation configuration interaction second-order perturbation (RI-CIS(D)) is studied. These methods can be applied to calculate transitions by using a reference determinant core-hole, they provide convenient approach compute large systems since all required states obtained within calculation, removing need...
The fluorescence of a two-dimensional supramolecular network 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) adsorbed on hexagonal boron nitride (hBN) is red-shifted due to, primarily, adsorbate-substrate van der Waals interactions. TCPP deposited from solution hBN and forms faceted islands with typical dimensions 100 nm either square or symmetry. molecular arrangement stabilized by in-plane hydrogen bonding as determined combination molecular-resolution atomic force microscopy...
Chiral molecules are widespread in nature, playing a fundamental role bio-chemical processes and the origin of life itself. The observation dynamics chiral is crucial for understanding control activity photo-excited states. One most promising techniques study systems time-resolved photoelectron circular dichroism (TR-PECD), which offers an intense sensitive probe vibronic geometric molecular structure as well electronic structures, their evolution on femtosecond timescale. However, non-local...
Of the many roles that solvent plays, its influence on molecular electronic structure is perhaps one of more challenging phenomena to study. In this study, effect solvation spectrum formamide investigated. Ab initio complete-active-space self-consistent field (CASSCF) and multiconfigurational second-order perturbation theory (CASPT2) methods are used compute ground- excited-state energies complexed with one, two, three water molecules. addition, a semicontinuum approach employed, in which...