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Donald G. Truhlar - One of the best experts on this subject based on the ideXlab platform.
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exploring the limit of accuracy of the global hybrid meta density functional for Main Group thermoChemistry kinetics and noncovalent interactions
Journal of Chemical Theory and Computation, 2008Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:The hybrid meta density functionals M05-2X and M06-2X have been shown to provide broad accuracy for Main Group Chemistry. In the present article we make the functional form more flexible and improve the self-interaction term in the correlation functional to improve its self-consistent-field convergence. We also explore the constraint of enforcing the exact forms of the exchange and correlation functionals through second order (SO) in the reduced density gradient. This yields two new functionals called M08-HX and M08-SO, with different exact constraints. The new functionals are optimized against 267 diverse Main-Group energetic data consisting of atomization energies, ionization potentials, electron affinities, proton affinities, dissociation energies, isomerization energies, barrier heights, noncovalent complexation energies, and atomic energies. Then the M08-HX, M08-SO, M05-2X, and M06-2X functionals and the popular B3LYP functional are tested against 250 data that were not part of the original training ...
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Density functionals with broad applicability in Chemistry.
Accounts of chemical research, 2008Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:Although density functional theory is widely used in the computational Chemistry community, the most popular density functional, B3LYP, has some serious shortcomings: (i) it is better for Main-Group Chemistry than for transition metals; (ii) it systematically underestimates reaction barrier heights; (iii) it is inaccurate for interactions dominated by medium-range correlation energy, such as van der Waals attraction, aromatic−aromatic stacking, and alkane isomerization energies. We have developed a variety of databases for testing and designing new density functionals. We used these data to design new density functionals, called M06-class (and, earlier, M05-class) functionals, for which we enforced some fundamental exact constraints such as the uniform-electron-gas limit and the absence of self-correlation energy. Our M06-class functionals depend on spin-up and spin-down electron densities (i.e., spin densities), spin density gradients, spin kinetic energy densities, and, for nonlocal (also called hybrid)...
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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
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assessment of density functionals for π systems energy differences between cumulenes and poly ynes proton affinities bond length alternation and torsional potentials of conjugated polyenes and proton affinities of conjugated shiff bases
Journal of Physical Chemistry A, 2006Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:Woodcock et al. (J. Phys. Chem. A 2002, 106, 11923) pointed out that no density functional was able to obtain the correct sign of the relative energies of the allene and propyne isomers of C3H4, and that DFT predicts that poly-ynes are insufficiently stabilized over cumulenes for higher homologs. In the present work we show that the recent M05 density functional predicts the correct ordering of allene and propyne and gives a mean unsigned error of only 1.8 kcal/mol for the relative energies of the two isomers of C3H4, C5H4, and C7H4. Two other recent functionals, M05-2X and PWB6K, also give reasonably low mean unsigned errors, 2.7 and 3.0 kcal/mol, respectively, as compared to 6.2 kcal/mol for the popular B3LYP functional. Another challenging problem for density functionals has been a tendency to overpolarize conjugated π systems. We test this here by considering proton affinities of conjugated polyenes and conjugated Schiff bases. Again M05-2X performs quite well, with mean unsigned errors of 2.1 and 3.9 kcal/mol, respectively, as compared to 5.8 and 5.9 kcal/mol for B3LYP. Averaged over the three problems, M05-2X has a mean unsigned error (MUE) of 3.0 kcal/mol, the BMK functional of Boese et al. has an MUE of 3.2 kcal/mol, and M05 has an MUE of 5.1 kcal/mol. Twenty-two other tested functionals have MUEs of 5.2-8.1 kcal/mol averaged over the three test problems. Both M05 and M05-2X do quite well, compared to other density functionals, for torsion potentials in butadiene and styrene, and M05 does very well for bond length alternation in conjugated polyenes. Since the M05 functional has broad accuracy for Main Group and transition metal Chemistry, and M05-2X has broad accuracy for Main Group Chemistry, we conclude that significant progress is being made in improving the performance of DFT across a wide range of problem types.
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assessment of density functionals for π systems energy differences between cumulenes and poly ynes proton affinities bond length alternation and torsional potentials of conjugated polyenes and proton affinities of conjugated shiff bases
Journal of Physical Chemistry A, 2006Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:Woodcock et al. (J. Phys. Chem. A 2002, 106, 11923) pointed out that no density functional was able to obtain the correct sign of the relative energies of the allene and propyne isomers of C3H4, and that DFT predicts that poly-ynes are insufficiently stabilized over cumulenes for higher homologs. In the present work we show that the recent M05 density functional predicts the correct ordering of allene and propyne and gives a mean unsigned error of only 1.8 kcal/mol for the relative energies of the two isomers of C3H4, C5H4, and C7H4. Two other recent functionals, M05-2X and PWB6K, also give reasonably low mean unsigned errors, 2.7 and 3.0 kcal/mol, respectively, as compared to 6.2 kcal/mol for the popular B3LYP functional. Another challenging problem for density functionals has been a tendency to overpolarize conjugated π systems. We test this here by considering proton affinities of conjugated polyenes and conjugated Schiff bases. Again M05-2X performs quite well, with mean unsigned errors of 2.1 and 3.9 kcal/mol, respectively, as compared to 5.8 and 5.9 kcal/mol for B3LYP. Averaged over the three problems, M05-2X has a mean unsigned error (MUE) of 3.0 kcal/mol, the BMK functional of Boese et al. has an MUE of 3.2 kcal/mol, and M05 has an MUE of 5.1 kcal/mol. Twenty-two other tested functionals have MUEs of 5.2-8.1 kcal/mol averaged over the three test problems. Both M05 and M05-2X do quite well, compared to other density functionals, for torsion potentials in butadiene and styrene, and M05 does very well for bond length alternation in conjugated polyenes. Since the M05 functional has broad accuracy for Main Group and transition metal Chemistry, and M05-2X has broad accuracy for Main Group Chemistry, we conclude that significant progress is being made in improving the performance of DFT across a wide range of problem types.
Yan Zhao - One of the best experts on this subject based on the ideXlab platform.
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exploring the limit of accuracy of the global hybrid meta density functional for Main Group thermoChemistry kinetics and noncovalent interactions
Journal of Chemical Theory and Computation, 2008Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:The hybrid meta density functionals M05-2X and M06-2X have been shown to provide broad accuracy for Main Group Chemistry. In the present article we make the functional form more flexible and improve the self-interaction term in the correlation functional to improve its self-consistent-field convergence. We also explore the constraint of enforcing the exact forms of the exchange and correlation functionals through second order (SO) in the reduced density gradient. This yields two new functionals called M08-HX and M08-SO, with different exact constraints. The new functionals are optimized against 267 diverse Main-Group energetic data consisting of atomization energies, ionization potentials, electron affinities, proton affinities, dissociation energies, isomerization energies, barrier heights, noncovalent complexation energies, and atomic energies. Then the M08-HX, M08-SO, M05-2X, and M06-2X functionals and the popular B3LYP functional are tested against 250 data that were not part of the original training ...
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Density functionals with broad applicability in Chemistry.
Accounts of chemical research, 2008Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:Although density functional theory is widely used in the computational Chemistry community, the most popular density functional, B3LYP, has some serious shortcomings: (i) it is better for Main-Group Chemistry than for transition metals; (ii) it systematically underestimates reaction barrier heights; (iii) it is inaccurate for interactions dominated by medium-range correlation energy, such as van der Waals attraction, aromatic−aromatic stacking, and alkane isomerization energies. We have developed a variety of databases for testing and designing new density functionals. We used these data to design new density functionals, called M06-class (and, earlier, M05-class) functionals, for which we enforced some fundamental exact constraints such as the uniform-electron-gas limit and the absence of self-correlation energy. Our M06-class functionals depend on spin-up and spin-down electron densities (i.e., spin densities), spin density gradients, spin kinetic energy densities, and, for nonlocal (also called hybrid)...
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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
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assessment of density functionals for π systems energy differences between cumulenes and poly ynes proton affinities bond length alternation and torsional potentials of conjugated polyenes and proton affinities of conjugated shiff bases
Journal of Physical Chemistry A, 2006Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:Woodcock et al. (J. Phys. Chem. A 2002, 106, 11923) pointed out that no density functional was able to obtain the correct sign of the relative energies of the allene and propyne isomers of C3H4, and that DFT predicts that poly-ynes are insufficiently stabilized over cumulenes for higher homologs. In the present work we show that the recent M05 density functional predicts the correct ordering of allene and propyne and gives a mean unsigned error of only 1.8 kcal/mol for the relative energies of the two isomers of C3H4, C5H4, and C7H4. Two other recent functionals, M05-2X and PWB6K, also give reasonably low mean unsigned errors, 2.7 and 3.0 kcal/mol, respectively, as compared to 6.2 kcal/mol for the popular B3LYP functional. Another challenging problem for density functionals has been a tendency to overpolarize conjugated π systems. We test this here by considering proton affinities of conjugated polyenes and conjugated Schiff bases. Again M05-2X performs quite well, with mean unsigned errors of 2.1 and 3.9 kcal/mol, respectively, as compared to 5.8 and 5.9 kcal/mol for B3LYP. Averaged over the three problems, M05-2X has a mean unsigned error (MUE) of 3.0 kcal/mol, the BMK functional of Boese et al. has an MUE of 3.2 kcal/mol, and M05 has an MUE of 5.1 kcal/mol. Twenty-two other tested functionals have MUEs of 5.2-8.1 kcal/mol averaged over the three test problems. Both M05 and M05-2X do quite well, compared to other density functionals, for torsion potentials in butadiene and styrene, and M05 does very well for bond length alternation in conjugated polyenes. Since the M05 functional has broad accuracy for Main Group and transition metal Chemistry, and M05-2X has broad accuracy for Main Group Chemistry, we conclude that significant progress is being made in improving the performance of DFT across a wide range of problem types.
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assessment of density functionals for π systems energy differences between cumulenes and poly ynes proton affinities bond length alternation and torsional potentials of conjugated polyenes and proton affinities of conjugated shiff bases
Journal of Physical Chemistry A, 2006Co-Authors: Yan Zhao, Donald G. TruhlarAbstract:Woodcock et al. (J. Phys. Chem. A 2002, 106, 11923) pointed out that no density functional was able to obtain the correct sign of the relative energies of the allene and propyne isomers of C3H4, and that DFT predicts that poly-ynes are insufficiently stabilized over cumulenes for higher homologs. In the present work we show that the recent M05 density functional predicts the correct ordering of allene and propyne and gives a mean unsigned error of only 1.8 kcal/mol for the relative energies of the two isomers of C3H4, C5H4, and C7H4. Two other recent functionals, M05-2X and PWB6K, also give reasonably low mean unsigned errors, 2.7 and 3.0 kcal/mol, respectively, as compared to 6.2 kcal/mol for the popular B3LYP functional. Another challenging problem for density functionals has been a tendency to overpolarize conjugated π systems. We test this here by considering proton affinities of conjugated polyenes and conjugated Schiff bases. Again M05-2X performs quite well, with mean unsigned errors of 2.1 and 3.9 kcal/mol, respectively, as compared to 5.8 and 5.9 kcal/mol for B3LYP. Averaged over the three problems, M05-2X has a mean unsigned error (MUE) of 3.0 kcal/mol, the BMK functional of Boese et al. has an MUE of 3.2 kcal/mol, and M05 has an MUE of 5.1 kcal/mol. Twenty-two other tested functionals have MUEs of 5.2-8.1 kcal/mol averaged over the three test problems. Both M05 and M05-2X do quite well, compared to other density functionals, for torsion potentials in butadiene and styrene, and M05 does very well for bond length alternation in conjugated polyenes. Since the M05 functional has broad accuracy for Main Group and transition metal Chemistry, and M05-2X has broad accuracy for Main Group Chemistry, we conclude that significant progress is being made in improving the performance of DFT across a wide range of problem types.
Karl O Christe - One of the best experts on this subject based on the ideXlab platform.
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unprecedented conformational variability in Main Group inorganic Chemistry the tetraazidoarsenite and antimonite salts a m n3 4 a nme4 pph4 ph3p 2n m as sb five similar salts five different anion structures
Inorganic Chemistry, 2013Co-Authors: Ralf Haiges, Martin Rahm, Karl O ChristeAbstract:A unique example for conformational variability in inorganic Main Group Chemistry has been discovered. The arrangement of the azido ligands in the pseudotrigonal bipyramidal [As(N3)4]− and [Sb(N3)4]− anions theoretically can give rise to seven different conformers which have identical MN4 skeletons but different azido ligand arrangements and very similar energies. We have now synthesized and structurally characterized five of these conformers by subtle variations in the nature of the counterion. Whereas conformational variability is common in organic Chemistry, it is rare in inorganic Main Group Chemistry and is usually limited to two. To our best knowledge, the experimental observation of five distinct single conformers for the same type of anion is unprecedented. Theoretical calculations at the M06-2X/cc-pwCVTZ-PP level for all seven possible basic conformers show that (1) the energy differences between the five experimentally observed conformers are about 1 kcal/mol or less, and (2) the free monomeric anions are the energetically favored species in the gas phase and also for [As(N3)4]− in the solid state, whereas for [Sb(N3)4]− associated anions are energetically favored in the solid state and possibly in solutions. Raman spectroscopy shows that in the azide antisymmetric stretching region, the solid-state spectra are distinct for the different conformers, and permits their identification. The spectra of solutions are solvent dependent and differ from those of the solids indicating the presence of rapidly exchanging equilibria of different conformers. The only compound for which a solid with a single well-ordered conformer could not be isolated was [N(CH3)4][As(N3)4] which formed a viscous, room-temperature ionic liquid. Its Raman spectrum was identical to that of its CH3CN solution indicating the presence of an equilibrium of multiple conformers.
Nathan E Schultz - One of the best experts on this subject based on the ideXlab platform.
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databases for transition element bonding metal metal bond energies and bond lengths and their use to test hybrid hybrid meta and meta density functionals and generalized gradient approximations
Journal of Physical Chemistry A, 2005Co-Authors: Nathan E SchultzAbstract:We propose a data set of bond lengths for 8 selected transition metal dimers (Ag(2), Cr(2), Cu(2), CuAg, Mo(2), Ni(2), V(2), and Zr(2)) and another data set containing their atomization energies and the atomization energy of ZrV, and we use these for testing density functional theory. The molecules chosen for the test sets were selected on the basis of the expected reliability of the data and their ability to constitute a diverse and representative set of transition element bond types while the data sets are kept small enough to allow for efficient testing of a large number of computational methods against a very reliable subset of experimental data. In this paper we test 42 different functionals: 2 local spin density approximation (LSDA) functionals, 12 generalized gradient approximation (GGA) methods, 13 hybrid GGAs, 7 meta GGA methods, and 8 hybrid meta GGAs. We find that GGA density functionals are more accurate for the atomization energies of pure transition metal systems than are their meta, hybrid, or hybrid meta analogues. We find that the errors for atomization energies and bond lengths are not as large if we limit ourselves to dimers with small amounts of multireference character. We also demonstrate the effects of increasing the fraction of Hartree-Fock exchange in multireference systems by computing the potential energy curve for Cr(2) and Mo(2) with several functionals. We also find that BLYP is the most accurate functional for bond energies and is reasonably accurate for bond lengths. The methods that work well for transition metal bonds are found to be quite different from those that work well for organic and other Main Group Chemistry.
Cameron Jones - One of the best experts on this subject based on the ideXlab platform.
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Extremely bulky amido-Group 14 element chloride complexes: Potential synthons for low oxidation state Main Group Chemistry
Dalton Transactions, 2011Co-Authors: Jiaye Li, Andreas Stasch, Christian Schenk, Cameron JonesAbstract:The preparation of a series of extremely bulky secondary amines, Ar*N(H)SiR3 (Ar* = C6H2{C(H)Ph2}2Me-2,6,4; R3 = Me3, MePh2 or Ph3) is described. Their deprotonation with either LiBun, NaH or KH yields alkali metal amide complexes, several monomeric examples of which, [Li(L){N(SiMe3)(Ar*)}] (L = OEt2 or THF), [Na(THF)3{N(SiMe3)(Ar*)}] and [K(OEt2){N(SiPh3)(Ar*)], have been crystallographically characterised. Reactions of the lithium amides with germanium, tin or lead dichloride have yielded the first structurally characterised two-coordinate, monomeric amido germanium(II) and tin(II) chloride complexes, [{(SiR3)(Ar*)N}ECl] (E = Ge or Sn; R = Me or Ph), and a chloride bridged amido-lead(II) dimer, [{[(SiMe3)(Ar*)N]Pb(μ-Cl)}2]. DFT calculations on [{(SiMe3)(Ar*)N}GeCl] show its HOMO to exhibit Ge lone pair character and its LUMO to encompass its Ge based p-orbital. A series of bulky amido silicon(IV) chloride complexes have also been prepared and several examples, [{(SiR3)(Ar*)N}SiCl3] (R3 = Me3, MePh2) and [{(SiMe3)(Ar*)N}SiHCl2], were crystallographically characterised. The sterically hindered Group 14 complexes reported in this study hold significant potential as precursors for kinetically stabilised low oxidation state and/or low coordination number Group 14 complexes.
