Contribution of triple substitutions to the electron correlation energy in fourth order perturbation theory

Krishnan, R.; Frisch, Michael J.; Pople, John A.

doi:10.1063/1.439657

Cited by 1,212 publications

(342 citation statements)

References 12 publications

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“…21 Fourth-order perturbation theory (MP4SDQ) 22 was used for some large complexes that contain 3-4 H 2 molecules. The basis sets used were correlation consistent valence-triple-zeta (cc-pVTZ) 23 for Li, Be, Na, and Mg and augmented aug-cc-pVTZ [24][25][26] for the other metal atoms and hydrogen.…”

Section: Methods Of Calculationmentioning

confidence: 99%

Structure and Stability of M−H₂ Complexes

Chaban

Gordon

1996

J. Phys. Chem.

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The potential stability of van der Waals complexes M−H2 (M = Li, Be, B, C, Na, Mg, Al, Si) is assessed using quadratic configuration interaction and large basis sets. It is found that the alkali metals and alkaline earths form very weak complexes in their ground states, but much stronger complexes in their (p) excited states. The elements B, Al, C, and Si form both linear (C∞v) and perpendicular (C2v) complexes, with greater thermodynamic stability in the latter arrangements. The complexes formed by C are likely to be kinetically unstable, and the same may be the case for Si. On the other hand, the complexes formed by B and Al are predicted to be quite stable. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: June 20, 1995; In Final Form: September 6, 1995 X The potential stability of van der Waals complexes M-H 2 (M ) Li, Be, B, C, Na, Mg, Al, Si) is assessed using quadratic configuration interaction and large basis sets. It is found that the alkali metals and alkaline earths form very weak complexes in their ground states, but much stronger complexes in their (p) excited states. The elements B, Al, C, and Si form both linear (C ∞V ) and perpendicular (C 2V ) complexes, with greater thermodynamic stability in the latter arrangements. The complexes formed by C are likely to be kinetically unstable, and the same may be the case for Si. On the other hand, the complexes formed by B and Al are predicted to be quite stable.

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Section: Methods Of Calculationmentioning

confidence: 99%

Structure and Stability of M−H₂ Complexes

Chaban

Gordon

1996

J. Phys. Chem.

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“…This is generally referred to as MP2. 33 The stationary points determined in this manner were verified to be local minima or transition states by computing and then diagonalizing the matrix of energy second derivatives (Hessian). This was accomplished by using the analytic derivative codes in GAMESS 34 and GAUSSIAN 92.…”

Section: Methodsmentioning

confidence: 99%

Ab Initio Molecular Orbital Investigation of the Unimolecular Decomposition of CH3SiH2+

Gordon¹,

Pederson²,

Bakhtiar³

et al. 1995

J. Phys. Chem.

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The potential energy surface for the decomposition of CH3SiH2+ was studied by ub initio electronic structure theory. At the MP2/6-31G(d,p) level of theory, CH3SiH2+ is the only minimum energy structure on the SiCH5+ potential energy surface. Lower levels of theory reported that +CH2SiH3 was also a local minimum, about 40 kcal/mol higher in energy with only a small (ca. 1-2 kcdmol) banier for conversion back to CH3SiH2+. However, at higher levels of theory, the C, structure of +CHzSiH3 has an imaginary frequency, indicating that it is a saddle point rather than a local minimum on the potential energy surface. The 0 K reaction enthalpies for 1,1 -dehydrogenation from silicon, 1,2-dehydrogenation, 1,l -dehydrogenation from carbon, and demethanation were calculated to be 30.2,69.1, 107.3, and 45.3 kcdmol, respectively. Activation energies (0 K) were calculated at the MP4/6-311++G(2df,2pd) level of theory with the classical barriers subsequently adjusted for zero-point vibrational energies. The 0 K activation energies for 1,l-dehydrogenation from silicon, l,Zdehydrogenation, and demethanation are predicted to be 66.6, 72.7, and 73.0 kcavmol, respectively. All attempts to locate a transition state for the insertion of the carbene-like species, CHSiHZ+, into Hz (reverse of the 1,l-dehydrogenation from carbon) were unsuccessful. This is not surprising since analogous carbene insertions are known to occur without a barrier. Thus, we conclude that this 1,l-H2 elimination from carbon proceeds monotonically uphill. The closed-shell structures for the products of the above reactions (CH3Si+, CH2SiH+, and CHSiH2+) were calculated at the MP2/6-31G(p,d) level of theory. Finally, triplet products were also examined. Disciplines Chemistry CommentsReprinted ( June 28, 1994; In Final Form: October 19, 1994° The potential energy surface for the decomposition of CH3SiHz + was studied by ab initio electronic structure theory. At the MP2/6-31G(d,p) level of theory, CH 3 SiHz+ is the only minimum energy structure on the SiCHs + potential energy surface. Lower levels of theory reported that +cHzSiH 3 was also a local minimum, about 40 kcaVmol higher in energy with only a small (ca. 1-2 kcaVmol) barrier for conversion back to CH3SiHz+. However, at higher levels of theory, the c. structure of +cHzSiH3 has an imaginary frequency, indicating that it is a saddle point rather than a local minimum on the potential energy surface. The 0 K reaction enthalpies for 1, !-dehydrogenation from silicon, 1 ,2-dehydrogenation, 1, !-dehydrogenation from carbon, and demethanation were calculated to be 30.2, 69.1, 107.3, and 45.3 kcaVmol, respectively. Activation energies (0 K) were calculated at the MP4/6-311 ++G(2df,2pd) level of theory with the classical barriers subsequently adjusted for zero-point vibrational energies. The 0 K activation energies for !,!-dehydrogenation from silicon, 1,2-dehydrogenation, and demethanation are predicted to be 66.6, 72.7, and 73.0 kcaVmol, respectively. All attempts to locate a transition state for the insert...

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“…the structure with the largest S 2 value of 0.89 corresponds to structure [t] in Figure 1. The UMP2/6-31 l+G(2df,2p) structures were treated with higher level correlation techniques including full fouith-order (SDTQ) PUMP4 (Krishnan and Pople 1978;Krishnan, Frisch, and Pople 1980) and QCISD(T) (Pople, Head-Gordon, and Raghavachari 1987) to generate single-point energies for all poirts on the PES. These PUMP4 and QCISD(T) results will be called "refined energies."…”

Section: Methodsmentioning

confidence: 99%

“…and trans-barriers compared to the PUMP4 separation for the 6-31 1+G(2df.2p) basis. This could attribute to the "often unsatisfactory" convergence of the MP series (Krishnan, Frisch, and Pople 1980).…”

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confidence: 99%

Ab Initio Potential Energy Surface for H + OCS Reactions: Extended Basis Sets and Correlation Treatment

Rice¹,

Chabalowski²

1994

J. Phys. Chem.

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Contribution of triple substitutions to the electron correlation energy in fourth order perturbation theory

Cited by 1,212 publications

References 12 publications

Structure and Stability of M−H₂ Complexes

Structure and Stability of M−H₂ Complexes

Ab Initio Molecular Orbital Investigation of the Unimolecular Decomposition of CH3SiH2+

Ab Initio Potential Energy Surface for H + OCS Reactions: Extended Basis Sets and Correlation Treatment

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Contribution of triple substitutions to the electron correlation energy in fourth order perturbation theory

Cited by 1,212 publications

References 12 publications

Structure and Stability of M−H2 Complexes

Structure and Stability of M−H2 Complexes

Ab Initio Molecular Orbital Investigation of the Unimolecular Decomposition of CH3SiH2+

Ab Initio Potential Energy Surface for H + OCS Reactions: Extended Basis Sets and Correlation Treatment

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Product

Resources

About

Structure and Stability of M−H₂ Complexes

Structure and Stability of M−H₂ Complexes