Computation of potential energy surfaces with the multireference correlation consistent composite approach

Mintz, Benjamin; Williams, T. Gavin; Howard, Levi; Wilson, Angela K.

doi:10.1063/1.3149387

Cited by 38 publications

(35 citation statements)

References 95 publications

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“…59 This formalism has been utilized recently by Mintz et al to study the potential energy surfaces of C 2 and N 2 and resulted in good agreement for their reaction coordinates, which are particularly multireference in the vicinity of the dissociation asymptote. 60 Due to the size of the copper nitrene system and the computational demand of the AQCC calculation, the active space chosen for all MR calculations was four electrons in five orbitals. Previous calculations by Dinescu et al on copper-nitrene complexes indicated that CASSCF active spaces of this size were suitable for modeling the different low-energy electronic states.…”

Section: Methodsmentioning

confidence: 99%

Activation of Carbon−Hydrogen and Hydrogen−Hydrogen Bonds by Copper−Nitrenes: A Comparison of Density Functional Theory with Single- and Multireference Correlation Consistent Composite Approaches

Tekarli

Williams

Cundari

2009

J. Chem. Theory Comput.

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Abstract:The kinetics and thermodynamics of copper-mediated nitrene insertion into C-H and H-H bonds (the former of methane) have been studied using several levels of theory: B3LYP/6-311++G(d,p), B97-1/cc-pVTZ, PBE1KCIS/cc-pVTZ, and ccCA (correlation consistent Composite Approach). The results show no significant difference among the DFT methods. All three DFT methods predict the ground state of the copper-nitrene model complex, L′Cu(NH), to be a triplet, while single reference ccCA predicts the singlet to be the ground state. The contributions to the total ccCA energy indicate that the singlet state is favored at the MP2/CBS level of theory, while electron correlation beyond this level (CCSD(T)) favors a triplet state, resulting in a close energetic balance between the two states. A multireference ccCA method is applied to the nitrene active species and supports the assignment of a singlet ground state. In general, the largest difference in the model reaction cycles between DFT and ccCA methods is for processes involving radicals and bond dissociation.

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Section: Methodsmentioning

confidence: 99%

Activation of Carbon−Hydrogen and Hydrogen−Hydrogen Bonds by Copper−Nitrenes: A Comparison of Density Functional Theory with Single- and Multireference Correlation Consistent Composite Approaches

Tekarli

Williams

Cundari

2009

J. Chem. Theory Comput.

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“…35 Along the dissociation path, this core contribution changes however by rather small amounts compared to the valence correlation changes. 39,43 Moreover, while Dunning's valence correlation-consistent cc-pVXZ basis sets 44 were appropriate for the recovery of the valence correlation energy, the more elaborate cc-pCVXZ core-valence basis sets of Dunning and co-workers 45 must be used to calculate core correlation effects. 33 The method must be based though on a multiconfigurational reference function that is capable of properly representing the dissociation without deterioration at stretched geometries.…”

Section: A Correlation Energy Contributions Involving Core Electronsmentioning

confidence: 99%

Accurate ab initio potential energy curve of O2. II. Core-valence correlations, relativistic contributions, and vibration-rotation spectrum

Bytautas

Matsunaga

Ruedenberg

2010

The Journal of Chemical Physics

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In the first paper of this series, a very accurate ab initio potential energy curve of the (3)Sigma(g)(-) ground state of O(2) has been determined in the approximation that all valence shell electron correlations were calculated at the complete basis set limit. In the present study, the corrections arising from core electron correlations and relativity effects, viz., spin-orbit coupling and scalar relativity, are determined and added to the potential energy curve. From the 24 points calculated on this curve, an analytical expression in terms of even-tempered Gaussian functions is determined and, from it, the vibrational and rotational energy levels are calculated by means of the discrete variable representation. We find 42 vibrational levels. Experimental data (from the Schumann-Runge band system) only yield the lowest 36 levels due to significant reduction in the transition intensities of higher levels. For the 35 term values G(v), the mean absolute deviation between theoretical and experimental data is 12.8 cm(-1). The dissociation energy with respect to the lowest vibrational energy is calculated within 25 cm(-1) of the experimental value of 41,268.2+/-3 cm(-1). The theoretical crossing between the (3)Sigma(g)(-) state and the (1)Sigma(g)(+) state is found to occur at 2.22 A and the spin-orbit coupling in this region is analyzed.

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“…[4][5][6][7]11 Recently, Mintz et al 12 have applied the multireference ccCA method 13 to compute the potential energy curves of N 2 and C 2 ; they obtained errors of ∼0.06 pm for the bond lengths and ∼2 cm −1 for the harmonic frequencies.…”

Section: Introductionmentioning

confidence: 99%

Performance of W4 theory for spectroscopic constants and electrical properties of small molecules

Karton

Martin

2010

The Journal of Chemical Physics

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Accurate spectroscopic constants and electrical properties of small molecules are determined by means of W4 and post-W4 theories. For a set of 28 first-and second-row diatomic molecules for which very accurate experimental spectroscopic constants are available, W4 theory affords near-spectroscopic or better predictions. Specifically, the root-mean-square deviations (RMSD) from experiment are 0.04 pm for the equilibrium bond distances (r e ), 1.03 cm −1 for the harmonic frequencies (ω e ), 0.20 cm −1 for the first anharmonicity constants (ω e x e ), 0.10 cm −1 for the second anharmonicity constants (ω e y e ), and 0.001 cm −1 for the vibration-rotation coupling constants (α e ).These RMSD imply 95% confidence intervals of about 0.1 pm for r e , 2.0 cm −1 for ω e , 0.4 cm −1 for ω e x e , and 0.2 cm −1 for ω e y e . We find that post-CCSD(T) contributions are essential to achieve such narrow confidence intervals for r e and ω e , but have little effect on ω e x e and α e , and virtually none on ω e y e . Higher-order connected triples,T 3 −(T), improve agreement with experiment for the hydride systems, but their inclusion (in the absence ofT 4 ) tends to worsen agreement with experiment for the nonhydride systems. Connected quadruple excitations,T 4 , have significant and systematic effects on r e , ω e , and ω e x e , in particular they universally increase r e (by up to 0.5 pm), universally reduce ω e (by up to 32 cm −1 ), and universally increase ω e x e (by up to 1 cm −1 ).Connected quintuple excitations,T 5 , are spectroscopically significant for ω e of the nonhydride systems, affecting ω e by up to 4 cm −1 . Diagonal Born-Oppenheimer corrections have systematic and spectroscopically-significant effects on r e and ω e of the hydride systems, universally increasing r e by 0.01-0.06 pm and decreasing ω e by 0.3-2.1 cm −1 . Obtaining r e and ω e of the pathologically multireference BN and BeO systems with near-spectroscopic accuracy requires large basis sets in the core-valence CCSD(T) step and augmented basis sets in the valence post-CCSD(T) steps in W4 theory. The triatomic molecules H 2 O, CO 2 , and O 3 are also considered. The equilibrium geometries and harmonic frequencies (with the exception of the asymmetric stretch of O 3 ) are obtained with near-spectroscopic accuracy at the W4 level. The asymmetric stretch of ozone represents a severe challenge to W4 theory, in particular the connected quadruple contribution converges very slowly with the basis set size. Finally, the importance of post-CCSD(T) correlation effects for electrical properties, namely dipole moments (µ), polarizabilities (α), and first hyperpolarizabilities (β) is evaluated.2

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Computation of potential energy surfaces with the multireference correlation consistent composite approach

Cited by 38 publications

References 95 publications

Activation of Carbon−Hydrogen and Hydrogen−Hydrogen Bonds by Copper−Nitrenes: A Comparison of Density Functional Theory with Single- and Multireference Correlation Consistent Composite Approaches

Activation of Carbon−Hydrogen and Hydrogen−Hydrogen Bonds by Copper−Nitrenes: A Comparison of Density Functional Theory with Single- and Multireference Correlation Consistent Composite Approaches

Accurate ab initio potential energy curve of O2. II. Core-valence correlations, relativistic contributions, and vibration-rotation spectrum

Performance of W4 theory for spectroscopic constants and electrical properties of small molecules

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