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Donald G Truhlar - One of the best experts on this subject based on the ideXlab platform.
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scaling exchange and correlation in the on top density functional of multiconfiguration pair density functional theory effect on Electronic Excitation energies and bond energies
Theoretical Chemistry Accounts, 2020Co-Authors: Davide Presti, Donald G Truhlar, Jan Kadlec, Laura GagliardiAbstract:Multiconfiguration pair-density functional (MC-PDFT) theory provides an economical way to calculate the ground-state and excited-state energetics of strongly correlated systems. The energy is calculated from the kinetic energy, density, and on-top pair-density of a multiconfiguration wave function as the sum of kinetic energy, classical Coulomb energy, and on-top density functional energy. We have usually found good results with the translated Perdew–Burke–Ernzerhof (tPBE) on-top density functional, and in this article, we examine whether the results can be systematically improved by introducing scaling constants into the exchange and correlation terms. We find that only a small improvement is possible for Electronic Excitation energies and that no improvement is possible for bond energies.
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revised m11 exchange correlation functional for Electronic Excitation energies and ground state properties
Journal of Physical Chemistry A, 2019Co-Authors: Pragya Verma, Ying Wang, Soumen Ghosh, Xiao He, Donald G TruhlarAbstract:The ability of Kohn–Sham density functional theory (KS-DFT) to accurately predict various types of Electronic Excitation energies with (necessarily approximate) exchange-correlation functionals faces several challenges. Chief among these is that valence Excitations are usually inherently multiconfigurational and therefore best treated by functionals with local exchange, whereas Rydberg and charge-transfer Excitations are often better treated with nonlocal exchange. The question arises regarding whether one can optimize a functional such that all three kinds of Excitations (valence, Rydberg, and charge transfer, including long-range charge transfer) are treated in a balanced and accurate way. The goal of the present work is to try to answer that question and then to optimize a functional with the best possible balanced behavior. Of the variety of functional types available, we choose to use a range-separated hybrid meta functional for the following reasons: (i) Range separation allows the percentage of Har...
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performance of the m11 and m11 l density functionals for calculations of Electronic Excitation energies by adiabatic time dependent density functional theory
Physical Chemistry Chemical Physics, 2012Co-Authors: Roberto Peverati, Donald G TruhlarAbstract:Adiabatic time-dependent density functional theory is a powerful method for calculating Electronic Excitation energies of complex systems, but the quality of the results depends on the choice of approximate density functional. In this article we test two promising new density functionals, M11 and M11-L, against databases of 214 diverse Electronic Excitation energies, and we compare the results to those for 16 other density functionals of various kinds and to time-dependent Hartree–Fock. Charge transfer Excitations are well known to be the hardest challenge for TDDFT. M11 is a long-range-corrected hybrid meta-GGA, and it shows better performance for charge transfer Excitations than any of the other functionals except M06-HF, which is a specialized functional that does not do well for valence Excitations. Several other long-range-corrected hybrid functionals also do well, and we especially recommend M11, ωB97X, and M06-2X for general spectroscopic applications because they do exceptionally well on ground-state properties as well as Excitation energies. Local functionals are preferred for many applications to extended systems because of their significant cost advantage for large systems. M11-L is a dual-range local functional and—unlike all previous local functionals—it has good performance for Rydberg states as well as for valence states. Thus it is highly recommended for Excitation energy calculations on extended systems.
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practical computation of Electronic Excitation in solution vertical Excitation model
Chemical Science, 2011Co-Authors: Aleksandr V Marenich, Donald G Truhlar, Christopher J Cramer, Ciro A Guido, Benedetta Mennucci, Giovanni Scalmani, Michael J FrischAbstract:We present a unified treatment of solvatochromic shifts in liquid-phase absorption spectra, and we develop a self-consistent state-specific vertical Excitation model (called VEM) for Electronic Excitation in solution. We discuss several other approaches to calculate vertical Excitations in solution as an approximation to VEM. We illustrate these methods by presenting calculations of the solvatochromic shifts of the lowest excited states of several solutes (acetone, acrolein, coumarin 153, indolinedimethine-malononitrile, julolidine-malononitrile, methanal, methylenecyclopropene, and pyridine) in polar and nonpolar solvents (acetonitrile, cyclohexane, dimethyl sulfoxide, methanol, n-hexane, n-pentane, and water) using implicit solvation models combined with configuration interaction based on single Excitations and with time-dependent density functional theory.
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sorting out the relative contributions of electrostatic polarization dispersion and hydrogen bonding to solvatochromic shifts on vertical Electronic Excitation energies
Journal of Chemical Theory and Computation, 2010Co-Authors: Aleksandr V Marenich, Christopher J Cramer, Donald G TruhlarAbstract:Conventional polarized continuum model calculations of solvatochromic shifts on Electronic Excitation energies using popular quantum chemical programs (e.g., Gaussian or Turbomole) include the noninertial and inertial bulk-solvent polarization, which will be called electrostatics, but not dispersion interactions and specific effects like hydrogen bonding. For the nf!* Excitation of acetone in several solvents, we estimated the nonelectrostatic contributions in two ways: (i) the vertical Excitation model (VEM) of Li et al. (Int. J. Quantum Chem.2000,77, 264), but updated to use TD-DFT corrected linear response with SMD atomic radii, and (ii) in the case of acetone in water, ensemble averaging over supermolecule calculations with up to 12 explicit solvent molecules selected from a molecular dynamics trajectory, with the explicit solvent surrounded by a continuum solvent. The TD-DFT VEM calculations carried out with the M06 density functional for 23 solvents result in a dispersion contribution to the red of 261-356 cm -1 and a hydrogen-bonding contribution to the blue of up to 289 cm -1 .
Hiroshi Nakatsuji - One of the best experts on this subject based on the ideXlab platform.
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symmetry adapted cluster and symmetry adapted cluster configuration interaction method in the polarizable continuum model theory of the solvent effect on the Electronic Excitation of molecules in solution
Journal of Chemical Physics, 2010Co-Authors: Roberto Cammi, Ryoichi Fukuda, Masahiro Ehara, Hiroshi NakatsujiAbstract:In this paper we present the theory and implementation of the symmetry-adapted cluster (SAC) and symmetry-adapted cluster-configuration interaction (SAC-CI) method, including the solvent effect, using the polarizable continuum model (PCM). The PCM and SAC/SAC-CI were consistently combined in terms of the energy functional formalism. The Excitation energies were calculated by means of the state-specific approach, the advantage of which over the linear-response approach has been shown. The single-point energy calculation and its analytical energy derivatives are presented and implemented, where the free-energy and its derivatives are evaluated because of the presence of solute-solvent interactions. We have applied this method to s-trans-acrolein and metylenecyclopropene of their Electronic Excitation in solution. The molecular geometries in the ground and excited states were optimized in vacuum and in solution, and both the vertical and adiabatic Excitations were studied. The PCM-SAC/SAC-CI reproduced the k...
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Electronic Excitation spectrum of thiophene studied by symmetry-adapted cluster configuration interaction method
Journal of Chemical Physics, 2001Co-Authors: Masahiko Hada, Masahiro Ehara, Hiroshi NakatsujiAbstract:Electronic Excitation spectrum of thiophene was investigated by the symmetry-adapted cluster (SAC)/SAC configuration interaction method. Seventy singlet and four lowest triplet Electronic states of thiophene were computed to give a detailed satisfactory theoretical interpretation of the vacuum ultraviolet (VUV) spectrum and the electron energy loss spectrum of thiophene. The present calculations gave the 2 1A1 valence state at 5.41 eV and the 1 1B2 valence state at 5.72 eV with oscillator strengths 0.0911 and 0.1131, respectively, and the 5 1A1 valence state at 7.32 eV and the 4 1B2 valence state at 7.40 eV with oscillator strengths 0.3614 and 0.1204, respectively. These valence-excited states were assigned to the two strong absorption bands of the VUV spectrum centered around 5.5 and 7.05 eV, respectively. A number of Rydberg transitions were obtained and assigned to the 6.0, 6.6, and 7.5–8.7 eV, etc. energy regions. The similarities and differences in the Electronic Excitations between thiophene and oth...
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Electronic Excitation spectra of furan and pyrrole: Revisited by the symmetry adapted cluster-configuration interaction method
Journal of Chemical Physics, 2000Co-Authors: Jaroslaw Meller, Masahiro Ehara, Masahiko Hada, Hiroshi NakatsujiAbstract:Electronic Excitation spectra of furan and pyrrole are reinvestigated by the symmetry-adapted cluster configuration-interaction method. The 47 and 46 lowest singlet and triplet Electronic states are computed for furan and pyrrole, respectively. Two series (1a2 and 2b1) of low-lying Rydberg states and the valence π–π* excited states strongly influence each other in both furan and pyrrole. The present calculations give detailed and satisfactory theoretical assignments of the vacuum ultraviolet spectra and the electron energy-loss spectra of the two molecules. The similarities and differences in the Electronic Excitations between furan and pyrrole are discussed in detail. The accuracy and assignments of recent theoretical studies, i.e., complete active space second-order perturbation, multireference Moller–Plesset perturbation, second-order algebraic-diagrammatic construction, multireference double configuration interaction, and CC3, are compared.
Paul M Danehy - One of the best experts on this subject based on the ideXlab platform.
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fiber coupled ultrashort pulse laser based Electronic Excitation tagging velocimetry
Applied Optics, 2018Co-Authors: Naibo Jiang, Paul M Danehy, James R GordAbstract:Transmission of intense ultrashort laser pulses through hollow-core fibers (HCFs) is investigated for molecular-tagging velocimetry. A low-vacuumed HCF beam-delivery system is developed to transmit high-peak-power pulses. Vacuum pressure effects on transmission efficiency and nonlinear effects at the fiber output are studied for 100 ps and 100 fs laser beams. With a 0.1 bar vacuum in the fiber, transmission efficiency increases by ∼30%, while spectral broadening is reduced. A 1 m long, 1 mm core metal-dielectric-coated HCF can transmit ∼45 mJ/pulse and ∼2.9 mJ/pulse for 100 ps laser pulses (at 532 nm) and 100 fs laser pulses (at 810 nm), respectively. Proof-of-principle, single-laser-shot, fiber-coupled, ps and fs laser-based, nitrogen Electronic-Excitation tagging velocimetry is demonstrated in a free jet. Flow velocities are measured at 200 kHz to capture high-frequency flow events.
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mixture fraction measurements with femtosecond laser Electronic Excitation tagging
Applied Optics, 2017Co-Authors: Benjamin R Halls, Naibo Jiang, James R Gord, Paul M DanehyAbstract:Tracer-free mixture-fraction measurements were demonstrated in a jet using femtosecond-laser Electronic-Excitation tagging. Measurements were conducted across a turbulent jet at several downstream locations both in a pure-nitrogen jet exiting into an air–nitrogen mixture and in a jet containing an air–nitrogen mixture exiting into pure nitrogen. The signal was calibrated with known concentrations of oxygen in nitrogen. The spatial resolution of the measurement was ∼180 μm. The measurement uncertainty ranged from 5% to 15%, depending on the mixture fraction and location within the beam, under constant temperature and pressure conditions. The measurements agree with a mixture fraction of unity within the potential core of the jet and transition to the self-similar region.
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seedless velocimetry at 100 khz with picosecond laser Electronic Excitation tagging
Optics Letters, 2017Co-Authors: Naibo Jiang, Hans U Stauffer, Jason G Mance, Mikhail N Slipchenko, Josef Felver, Tongxun Yi, Paul M DanehyAbstract:Picosecond-laser Electronic-Excitation tagging (PLEET), a seedless picosecond-laser-based velocimetry technique, is demonstrated in non-reactive flows at a repetition rate of 100 kHz with a 1064 nm, 100 ps burst-mode laser. The fluorescence lifetime of the PLEET signal was measured in nitrogen, and the laser heating effects were analyzed. PLEET experiments with a free jet of nitrogen show the ability to measure multi-point flow velocity fluctuations at a 100 kHz detection rate or higher. Both spectral and dynamic mode decomposition analyses of velocity on a Ma=0.8 free jet show two dominant Strouhal numbers around 0.24 and 0.48, respectively, well within the shear-layer flapping frequencies of the free jets. This technique increases the laser-tagging repetition rate for velocimetry to hundreds of kilohertz. PLEET is suitable for subsonic through supersonic laminar- and turbulent-flow velocity measurements.
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selective two photon absorptive resonance femtosecond laser Electronic Excitation tagging velocimetry
Optics Letters, 2016Co-Authors: Naibo Jiang, Benjamin R Halls, Hans U Stauffer, Paul M DanehyAbstract:Selective two-photon absorptive resonance femtosecond-laser Electronic-Excitation tagging (STARFLEET), a nonseeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and nonreactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25 nm 100 fs light. STARFLEET greatly reduces the per-pulse energy required (30 μJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and nonreactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities, and further demonstrate the significantly less intrusive nature of STARFLEET.
Roberto Cammi - One of the best experts on this subject based on the ideXlab platform.
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symmetry adapted cluster and symmetry adapted cluster configuration interaction method in the polarizable continuum model theory of the solvent effect on the Electronic Excitation of molecules in solution
Journal of Chemical Physics, 2010Co-Authors: Roberto Cammi, Ryoichi Fukuda, Masahiro Ehara, Hiroshi NakatsujiAbstract:In this paper we present the theory and implementation of the symmetry-adapted cluster (SAC) and symmetry-adapted cluster-configuration interaction (SAC-CI) method, including the solvent effect, using the polarizable continuum model (PCM). The PCM and SAC/SAC-CI were consistently combined in terms of the energy functional formalism. The Excitation energies were calculated by means of the state-specific approach, the advantage of which over the linear-response approach has been shown. The single-point energy calculation and its analytical energy derivatives are presented and implemented, where the free-energy and its derivatives are evaluated because of the presence of solute-solvent interactions. We have applied this method to s-trans-acrolein and metylenecyclopropene of their Electronic Excitation in solution. The molecular geometries in the ground and excited states were optimized in vacuum and in solution, and both the vertical and adiabatic Excitations were studied. The PCM-SAC/SAC-CI reproduced the k...
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Electronic Excitation energies of molecules in solution state specific and linear response methods for nonequilibrium continuum solvation models
Journal of Chemical Physics, 2005Co-Authors: Roberto Cammi, Benedetta Mennucci, Stefano Corni, Jacopo TomasiAbstract:We present a formal comparison between the two different approaches to the calculation of Electronic Excitation energies of molecules in solution within the continuum solvation model framework, taking also into account nonequilibrium effects. These two approaches, one based on the explicit evaluation of the excited state wave function of the solute and the other based on the linear response theory, are here proven to give formally different expressions for the Excitation energies even when exact eigenstates are considered. Calculations performed for some illustrative examples show that this formal difference has sensible effects on absolute solvatochromic shifts (i.e., with respect to gas phase) while it has small effects on relative (i.e., nonpolar to polar solvent) solvatochromic shifts.
A. M. Stoneham - One of the best experts on this subject based on the ideXlab platform.
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Materials modification by Electronic Excitation
Applied Surface Science, 2020Co-Authors: A. M. Stoneham, Noriaki ItohAbstract:AbstractElectronic Excitation by lasers or electron beams can modify the properties of materials. The changes are not just due to heat, nor do they result from the well-known collision dynamics of much radiation damage. Everyday examples of modification by Electronic Excitation include photography, and photochromics (such as sunglasses) which change colour. In the last few years it has become clear that Excitation can offer novel types of modification, with better-controlled changes. The field has evolved through a mix of basic science, of new laser and electron beam tools, and of new needs from microElectronics, photonics and nanotechnology. Underlying this development are some common themes which integrate the basic science and its applications. These include especially the ideas of energy localisation and charge localisation. There are detailed comparisons of experiment and theory for halides, but there is a wealth of information for other materials. From this, we identify ways to connect understanding to technological needs, like selective removal of material, controlled changes, altering the balance between process steps, and possibilities of quantum control. The field is reviewed in full in our recent book [N. Itoh, A.M. Stoneham, Materials Modification by Electronic Excitation, Cambridge University Press, Cambridge, 2000]
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making tracks Electronic Excitation roles in forming swift heavy ion tracks
Journal of Physics: Condensed Matter, 2009Co-Authors: N Itoh, Dorothy M Duffy, S Khakshouri, A. M. StonehamAbstract:Swift heavy ions cause material modification along their tracks, changes primarily due to their very dense Electronic Excitation. The available data for threshold stopping powers indicate two main classes of materials. Group I, with threshold stopping powers above about 10 keV nm −1 , includes some metals, crystalline semiconductors and a few insulators. Group II, with lower thresholds, comprises many insulators, amorphous materials and high Tc oxide superconductors. We show that the systematic differences in behaviour result from different coupling of the dense excited electrons, holes and excitons to atomic (ionic) motions, and the consequent lattice relaxation. The coupling strength of excitons and charge carriers with the lattice is crucial. For group II, the mechanism appears to be the self-trapped exciton model of Itoh and Stoneham (1998 Nucl. Instrum. Methods Phys. Res. B 146 362): the local structural changes occur roughly when the exciton concentration exceeds the number of lattice sites. In materials of group I, excitons are not self-trapped and structural change requires Excitation of a substantial fraction of bonding electrons, which induces spontaneous lattice expansion within a few hundred femtoseconds, as recently observed by laser-induced time-resolved x-ray diffraction of semiconductors. Our analysis addresses a number of experimental results, such as track morphology, the efficiency of track registration and the ratios of the threshold stopping power of various materials. (Some figures in this article are in colour only in the Electronic version) This paper celebrates the contribution made by Dr Richard Palmer to IOP Publishing, and especially to Journal of Physics: Condensed Matter.
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Making tracks: Electronic Excitation roles in forming swift heavy ion tracks
J PHYS-CONDENS MAT, 2009Co-Authors: A. M. StonehamAbstract:Swift heavy ions cause material modification along their tracks, changes primarily due to their very dense Electronic Excitation. The available data for threshold stopping powers indicate two main classes of materials. Group I, with threshold stopping powers above about 10 keV nm(-1), includes some metals, crystalline semiconductors and a few insulators. Group II, with lower thresholds, comprises many insulators, amorphous materials and high T-c oxide superconductors. We show that the systematic differences in behaviour result from different coupling of the dense excited electrons, holes and excitons to atomic (ionic) motions, and the consequent lattice relaxation. The coupling strength of excitons and charge carriers with the lattice is crucial. For group II, the mechanism appears to be the self- trapped exciton model of Itoh and Stoneham ( 1998 Nucl. Instrum. Methods Phys. Res. B 146 362): the local structural changes occur roughly when the exciton concentration exceeds the number of lattice sites. In materials of group I, excitons are not self- trapped and structural change requires Excitation of a substantial fraction of bonding electrons, which induces spontaneous lattice expansion within a few hundred femtoseconds, as recently observed by laser- induced time- resolved x- ray diffraction of semiconductors. Our analysis addresses a number of experimental results, such as track morphology, the efficiency of track registration and the ratios of the threshold stopping power of various materials.
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materials modification by Electronic Excitation
2000Co-Authors: N Itoh, A. M. StonehamAbstract:Abstract Excitonic mechanisms of defect formation and of sputtering from surfaces, induced as a consequence of exciton relaxation, are effective in a limited class of wide-gap materials, such as alkali halides, alkaline earth fluorides and fused quartz. In this paper, we point out that modification by Electronic Excitation can be achieved in a far wider range of materials. First, referring to STM observations of semiconductor surfaces irradiated by laser or intense-electron beams, we show that atomic emissions with Electronic origin do take place even in materials in which the bandgap energy is smaller than the energy to remove an atom from the surface. The yield of this process is linear with the beam intensity for higher incident energies, but superlinear for lower incident energies. Secondly we analyse the phenomena of laser damage and laser ablation in a variety of wide-gap materials, emphasizing the role played by defect creation in the bulk, and atomic emissions from surfaces originating from excita...