The Experts below are selected from a list of 5712 Experts worldwide ranked by ideXlab platform
Jan M L Martin - One of the best experts on this subject based on the ideXlab platform.
-
Economical Post-CCSD(T) Computational Thermochemistry Protocol and Applications to Some Aromatic Compounds †
2020Co-Authors: Amir Karton, Ilya Kaminker, Jan M L MartinAbstract:To achieve a kilojoules-per-mole level of accuracy consistently in computational Thermochemistry, the inclusion of post-CCSD(T) correlation effects cannot be avoided. Such effects are included in the W4 and HEAT computational Thermochemistry protocols. The principal bottleneck in carrying out such calculations for larger systems is the evaluation of the T 3 -(T) term. We propose a cost-effective empirical approximation for this term that does not entail any reliance on experimental data. For first-row molecules, our W3.2lite protocol yields atomization energies with a 95% confidence interval of ∼0.4 kcal/mol at the expense of introducing two such parameters. W3.2lite has been successfully applied to aromatic and aliphatic hydrocarbons such as benzene, fulvene, phenyl radical, pyridine, furan, benzyne isomers, trans-butadiene, cyclobutene, [1.1.1]propellane, and bicyclo[1.1.1]pentane. The W3.2lite predictions for fulvene, phenyl radical, cyclobutene, and [1.1.1]propellane are impossible to reconcile with experiment and suggest that remeasurement may be in order
-
dsd blyp a general purpose double hybrid density functional including spin component scaling and dispersion correction
Journal of Physical Chemistry C, 2010Co-Authors: Sebastian Kozuch, David Gruzman, Jan M L MartinAbstract:We present a general purpose double-hybrid DFT parametrization based on the BLYP functional, spin-component scaled (SCS) MP2-like correlation and a dispersion correction, called DSD-BLYP. Six training sets were used, including main group and transition state Thermochemistry, kinetics, and dispersion forces. This new parametrization is usually 10−15% more accurate than the already exceptional B2GP-PLYP double hybrid, at the same computational cost. Its principal benefit is greater robustness for systems with significant nondynamical correlation. If a scaling factor is included in the harmonic frequency calculations, B2GP-PLYP was found to give very accurate results for kinetics, Thermochemistry, and frequencies.
-
highly accurate first principles benchmark data sets for the parametrization and validation of density functional and other approximate methods derivation of a robust generally applicable double hybrid functional for Thermochemistry and thermochemica
Journal of Physical Chemistry A, 2008Co-Authors: Amir Karton, Alex Tarnopolsky, Jan M L Martin, Jean Francois Lamere, George C SchatzAbstract:We present a number of near-exact, nonrelativistic, Born-Oppenheimer reference data sets for the parametrization of more approximate methods (such as DFT functionals). The data were obtained by means of the W4 ab initio computational Thermochemistry protocol, which has a 95% confidence interval well below 1 kJ/mol. Our data sets include W4-08, which are total atomization energies of over 100 small molecules that cover varying degrees of nondynamical correlations, and DBH24-W4, which are W4 theory values for Truhlar's set of 24 representative barrier heights. The usual procedure of comparing calculated DFT values with experimental atomization energies is hampered by comparatively large experimental uncertainties in many experimental values and compounds errors due to deficiencies in the DFT functional with those resulting from neglect of relativity and finite nuclear mass. Comparison with accurate, explicitly nonrelativistic, ab initio data avoids these issues. We then proceed to explore the performance of B2x-PLYP-type double hybrid functionals for atomization energies and barrier heights. We find that the optimum hybrids for hydrogen-transfer reactions, heavy-atoms transfers, nucleophilic substitutions, and unimolecular and recombination reactions are quite different from one another: out of these subsets, the heavy-atom transfer reactions are by far the most sensitive to the percentages of Hartree-Fock-type exchange y and MP2-type correlation x in an (x, y) double hybrid. The (42,72) hybrid B2K-PLYP, as reported in a preliminary communication, represents the best compromise between Thermochemistry and hydrogen-transfer barriers, while also yielding excellent performance for nucleophilic substitutions. By optimizing for best overall performance on both Thermochemistry and the DBH24-W4 data set, however, we find a new (36,65) hybrid which we term B2GP-PLYP. At a slight expense in performance for hydrogen-transfer barrier heights and nucleophilic substitutions, we obtain substantially better performance for the other reaction types. Although both B2K-PLYP and B2GP-PLYP are capable of 2 kcal/mol quality Thermochemistry, B2GP-PLYP appears to be the more robust toward nondynamical correlation and strongly polar character. We additionally find that double-hybrid functionals display excellent performance for such problems as hydrogen bonding, prototype late transition metal reactions, pericyclic reactions, prototype cumulene-polyacetylene system, and weak interactions.
-
double hybrid functionals for thermochemical kinetics
Journal of Physical Chemistry A, 2008Co-Authors: Alex Tarnopolsky, Rotem Sertchook, Dana Vuzman, Amir Karton, Jan M L MartinAbstract:We propose two new double-hybrid functionals, denoted B2K-PLYP and mPW2K-PLYP, which yield thermochemical performance comparable to existing double-hybrid functionals but offer superior performance for barrier heights of various kinds. We show that the new functionals yield excellent performance for all of the following: (a) main-group Thermochemistry; (b) main-group thermochemical kinetics; (c) late transition metal reactions. In addition, B2K-PLYP performs well for weak interactions.
-
w4 Thermochemistry of p2 and p4 is the codata heat of formation of the phosphorus atom correct
Molecular Physics, 2007Co-Authors: Amir Karton, Jan M L MartinAbstract:The high-accuracy W4 computational Thermochemistry protocol, and several post-W4 methods, have been applied to the P2 and P4 molecules. Contrary to previous studies, we find the experimental Thermochemistry to be fundamentally sound. The reaction enthalpy for P4→2P 2 has a very significant contribution from post-CCSD(T) correlation effects. We derive a gas-phase heat of formation for the phosphorus atom of kcal mol−1 and kcal mol−1, in the upper half of the CODATA uncertainty interval.
Donald G. Truhlar - One of the best experts on this subject based on the ideXlab platform.
-
the m06 suite of density functionals for main group Thermochemistry thermochemical kinetics noncovalent interactions excited states and transition elements two new functionals and systematic testing of four m06 class functionals and 12 other functionals
Theoretical Chemistry Accounts, 2008Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:We present two new hybrid meta exchange- correlation functionals, called M06 and M06-2X. The M06 functional is parametrized including both transition metals and nonmetals, whereas the M06-2X functional is a high-nonlocality functional with double the amount of nonlocal exchange (2X), and it is parametrized only for nonmetals.The functionals, along with the previously published M06-L local functional and the M06-HF full-Hartree–Fock functionals, constitute the M06 suite of complementary functionals. We assess these four functionals by comparing their performance to that of 12 other functionals and Hartree–Fock theory for 403 energetic data in 29 diverse databases, including ten databases for Thermochemistry, four databases for kinetics, eight databases for noncovalent interactions, three databases for transition metal bonding, one database for metal atom excitation energies, and three databases for molecular excitation energies. We also illustrate the performance of these 17 methods for three databases containing 40 bond lengths and for databases containing 38 vibrational frequencies and 15 vibrational zero point energies. We recommend the M06-2X functional for applications involving main-group Thermochemistry, kinetics, noncovalent interactions, and electronic excitation energies to valence and Rydberg states. We recommend the M06 functional for application in organometallic and inorganometallic chemistry and for noncovalent interactions.
-
a new local density functional for main group Thermochemistry transition metal bonding thermochemical kinetics and noncovalent interactions
Journal of Chemical Physics, 2006Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:We present a new local density functional, called M06-L, for main-group and transition element Thermochemistry, thermochemical kinetics, and noncovalent interactions. The functional is designed to capture the main dependence of the exchange-correlation energy on local spin density, spin density gradient, and spin kinetic energy density, and it is parametrized to satisfy the uniform-electron-gas limit and to have good performance for both main-group chemistry and transition metal chemistry. The M06-L functional and 14 other functionals have been comparatively assessed against 22 energetic databases. Among the tested functionals, which include the popular B3LYP, BLYP, and BP86 functionals as well as our previous M05 functional, the M06-L functional gives the best overall performance for a combination of main-group Thermochemistry, thermochemical kinetics, and organometallic, inorganometallic, biological, and noncovalent interactions. It also does very well for predicting geometries and vibrational frequencies. Because of the computational advantages of local functionals, the present functional should be very useful for many applications in chemistry, especially for simulations on moderate-sized and large systems and when long time scales must be addressed. © 2006 American Institute of Physics. DOI: 10.1063/1.2370993
-
Design of density functionals that are broadly accurate for Thermochemistry, thermochemical kinetics, and nonbonded interactions.
The journal of physical chemistry. A, 2005Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:This paper develops two new hybrid meta exchange-correlation functionals for Thermochemistry, thermochemical kinetics, and nonbonded interactions. The new functionals are called PW6B95 (6-parameter...
-
Multi-coefficient extrapolated density functional theory for Thermochemistry and thermochemical kinetics
Physical Chemistry Chemical Physics, 2005Co-Authors: Yan Zhao, Benjamin J. Lynch, Donald G. TruhlarAbstract:We have developed a new kind of multi-coefficient correlation method (MCCM) by empirically mixing correlated wave function methods and density functional methods. The new methods constitute a generalization of hybrid density functional theory and may be called multi-coefficient extrapolated density functional theory. Results by the new methods are compared to those obtained by G3SX, G3SX(MP3), CBS-Q and MCCM/3 for calculations of atomization energies, barrier heights, ionization potentials and electron affinities. These results show that the multi-coefficient extrapolated density functional theory is more accurate for Thermochemistry and thermochemical kinetics than the pure wave function methods of comparable cost. As a byproduct of this work we optimized a new hybrid meta density functional theory called TPSS1KCIS, which has excellent performance for Thermochemistry.
Yan Zhao - One of the best experts on this subject based on the ideXlab platform.
-
the m06 suite of density functionals for main group Thermochemistry thermochemical kinetics noncovalent interactions excited states and transition elements two new functionals and systematic testing of four m06 class functionals and 12 other functionals
Theoretical Chemistry Accounts, 2008Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:We present two new hybrid meta exchange- correlation functionals, called M06 and M06-2X. The M06 functional is parametrized including both transition metals and nonmetals, whereas the M06-2X functional is a high-nonlocality functional with double the amount of nonlocal exchange (2X), and it is parametrized only for nonmetals.The functionals, along with the previously published M06-L local functional and the M06-HF full-Hartree–Fock functionals, constitute the M06 suite of complementary functionals. We assess these four functionals by comparing their performance to that of 12 other functionals and Hartree–Fock theory for 403 energetic data in 29 diverse databases, including ten databases for Thermochemistry, four databases for kinetics, eight databases for noncovalent interactions, three databases for transition metal bonding, one database for metal atom excitation energies, and three databases for molecular excitation energies. We also illustrate the performance of these 17 methods for three databases containing 40 bond lengths and for databases containing 38 vibrational frequencies and 15 vibrational zero point energies. We recommend the M06-2X functional for applications involving main-group Thermochemistry, kinetics, noncovalent interactions, and electronic excitation energies to valence and Rydberg states. We recommend the M06 functional for application in organometallic and inorganometallic chemistry and for noncovalent interactions.
-
a new local density functional for main group Thermochemistry transition metal bonding thermochemical kinetics and noncovalent interactions
Journal of Chemical Physics, 2006Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:We present a new local density functional, called M06-L, for main-group and transition element Thermochemistry, thermochemical kinetics, and noncovalent interactions. The functional is designed to capture the main dependence of the exchange-correlation energy on local spin density, spin density gradient, and spin kinetic energy density, and it is parametrized to satisfy the uniform-electron-gas limit and to have good performance for both main-group chemistry and transition metal chemistry. The M06-L functional and 14 other functionals have been comparatively assessed against 22 energetic databases. Among the tested functionals, which include the popular B3LYP, BLYP, and BP86 functionals as well as our previous M05 functional, the M06-L functional gives the best overall performance for a combination of main-group Thermochemistry, thermochemical kinetics, and organometallic, inorganometallic, biological, and noncovalent interactions. It also does very well for predicting geometries and vibrational frequencies. Because of the computational advantages of local functionals, the present functional should be very useful for many applications in chemistry, especially for simulations on moderate-sized and large systems and when long time scales must be addressed. © 2006 American Institute of Physics. DOI: 10.1063/1.2370993
-
Design of density functionals that are broadly accurate for Thermochemistry, thermochemical kinetics, and nonbonded interactions.
The journal of physical chemistry. A, 2005Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:This paper develops two new hybrid meta exchange-correlation functionals for Thermochemistry, thermochemical kinetics, and nonbonded interactions. The new functionals are called PW6B95 (6-parameter...
-
Multi-coefficient extrapolated density functional theory for Thermochemistry and thermochemical kinetics
Physical Chemistry Chemical Physics, 2005Co-Authors: Yan Zhao, Benjamin J. Lynch, Donald G. TruhlarAbstract:We have developed a new kind of multi-coefficient correlation method (MCCM) by empirically mixing correlated wave function methods and density functional methods. The new methods constitute a generalization of hybrid density functional theory and may be called multi-coefficient extrapolated density functional theory. Results by the new methods are compared to those obtained by G3SX, G3SX(MP3), CBS-Q and MCCM/3 for calculations of atomization energies, barrier heights, ionization potentials and electron affinities. These results show that the multi-coefficient extrapolated density functional theory is more accurate for Thermochemistry and thermochemical kinetics than the pure wave function methods of comparable cost. As a byproduct of this work we optimized a new hybrid meta density functional theory called TPSS1KCIS, which has excellent performance for Thermochemistry.
Martin Headgordon - One of the best experts on this subject based on the ideXlab platform.
-
how accurate are the minnesota density functionals for noncovalent interactions isomerization energies Thermochemistry and barrier heights involving molecules composed of main group elements
Journal of Chemical Theory and Computation, 2016Co-Authors: Narbe Mardirossian, Martin HeadgordonAbstract:The 14 Minnesota density functionals published between the years 2005 and early 2016 are benchmarked on a comprehensive database of 4986 data points (84 data sets) involving molecules composed of main-group elements. The database includes noncovalent interactions, isomerization energies, Thermochemistry, and barrier heights, as well as equilibrium bond lengths and equilibrium binding energies of noncovalent dimers. Additionally, the sensitivity of the Minnesota density functionals to the choice of basis set and integration grid is explored for both noncovalent interactions and Thermochemistry. Overall, the main strength of the hybrid Minnesota density functionals is that the best ones provide very good performance for Thermochemistry (e.g., M06-2X), barrier heights (e.g., M08-HX, M08-SO, MN15), and systems heavily characterized by self-interaction error (e.g., M06-2X, M08-HX, M08-SO, MN15), while the main weakness is that none of them are state-of-the-art for the full spectrum of noncovalent interactions ...
-
separate electronic attenuation allowing a spin component scaled second order moller plesset theory to be effective for both Thermochemistry and noncovalent interactions
Journal of Physical Chemistry B, 2014Co-Authors: Matthew Goldey, Martin HeadgordonAbstract:Spin-component-scaled (SCS) second-order Moller–Plesset perturbation theory (MP2) improves the treatment of Thermochemistry and noncovalent interactions relative to MP2, although the optimal scaling coefficients are quite different for Thermochemistry versus noncovalent interactions. This work reconciles these two different scaling regimes for SCS-MP2 by using two different length scales for electronic attenuation of the two spin components. The attenuation parameters and scaling coefficients are optimized in the aug-cc-pVTZ (aTZ) basis using the S66 database of intermolecular interactions and the W4-11 database of Thermochemistry. Transferability tests are performed for atomization energies and barrier heights, as well as on further test sets for inter- and intramolecular interactions. SCS dual-attenuated MP2 in the aTZ basis, SCS-MP2(2terfc, aTZ), performs similarly to SCS-MP2/aTZ for Thermochemistry while frequently outperforming MP2 at the complete basis set limit (CBS) for nonbonded interactions.
-
systematic optimization of long range corrected hybrid density functionals
Journal of Chemical Physics, 2008Co-Authors: Jengda Chai, Martin HeadgordonAbstract:A general scheme for systematically modeling long-range corrected (LC) hybrid density functionals is proposed. Our resulting two LC hybrid functionals are shown to be accurate in Thermochemistry, kinetics, and noncovalent interactions, when compared with common hybrid density functionals. The qualitative failures of the commonly used hybrid density functionals in some “difficult problems,” such as dissociation of symmetric radical cations and long-range charge-transfer excitations, are significantly reduced by the present LC hybrid density functionals.
John F Stanton - One of the best experts on this subject based on the ideXlab platform.
-
high accuracy extrapolated ab initio Thermochemistry iii additional improvements and overview
Journal of Chemical Physics, 2008Co-Authors: Michael E Harding, Jurgen Gauss, Branko Ruscic, Juana Vazquez, Angela K Wilson, John F StantonAbstract:Effects of increased basis-set size as well as a correlated treatment of the diagonal Born-Oppenheimer approximation are studied within the context of the high-accuracy extrapolated ab initio Thermochemistry (HEAT) theoretical model chemistry. It is found that the addition of these ostensible improvements does little to increase the overall accuracy of HEAT for the determination of molecular atomization energies. Fortuitous cancellation of high-level effects is shown to give the overall HEAT strategy an accuracy that is, in fact, higher than most of its individual components. In addition, the issue of core-valence electron correlation separation is explored; it is found that approximate additive treatments of the two effects have limitations that are significant in the realm of <1kJmol−1 theoretical Thermochemistry.
-
high accuracy extrapolated ab initio Thermochemistry ii minor improvements to the protocol and a vital simplification
Journal of Chemical Physics, 2006Co-Authors: Yannick J Bomble, Peter G Szalay, Mihaly Kallay, Jurgen Gauss, Attila G Csaszar, Juana Vazquez, Christine Michauk, John F StantonAbstract:The recently developed high-accuracy extrapolated ab initio Thermochemistry method for theoretical Thermochemistry, which is intimately related to other high-precision protocols such as the Weizmann-3 and focal-point approaches, is revisited. Some minor improvements in theoretical rigor are introduced which do not lead to any significant additional computational overhead, but are shown to have a negligible overall effect on the accuracy. In addition, the method is extended to completely treat electron correlation effects up to pentuple excitations. The use of an approximate treatment of quadruple and pentuple excitations is suggested; the former as a pragmatic approximation for standard cases and the latter when extremely high accuracy is required. For a test suite of molecules that have rather precisely known enthalpies of formation {as taken from the active thermochemical tables of Ruscic and co-workers [Lecture Notes in Computer Science, edited by M. Parashar (Springer, Berlin, 2002), Vol. 2536, pp. 25...
-
benchmark Thermochemistry of the hydroperoxyl radical
Journal of Physical Chemistry A, 2004Co-Authors: Bradley A Flowers, Peter G Szalay, John F Stanton, Mihaly Kallay, Jurgen Gauss, Attila G CsaszarAbstract:A theoretical estimation of the enthalpy of formation for the hydroperoxyl radical is presented. These results are based on CCSD(T)/aug-cc-pCV5Z calculations extrapolated to the basis-set limit with additional corrections. Anharmonic vibrational zero-point energies, scalar relativistic, spin -orbit coupling, and diagonal BornOppenheimer corrections are further used to correct the extrapolated term energies, as well as various empirical corrections that account for correlation effects not treated at the CCSD(T) level. We estimate that ¢fH° ) 3.66 ( 0.10 kcal mol -1 (¢fH° ) 2.96 ( 0.10 kcal mol -1 ) using several reaction schemes. Significantly, it appears to be necessary to include effects of connected pentuple excitations in order to achieve an uncertainty of ca. 0.1 kcal mol -1 .
