Hybrid correlation models based on active-space partitioning: correcting second-order Moller-Plesset perturbation theory for bond-breaking reactions.

Hybrid correlation models based on active-space partitioning: seeking accurate O(N5) ab initio methods for bond breaking.

Moller-Plesset second-order (MP2) perturbation theory remains the least expensive standard ab initio method that includes electron correlation, scaling as O(N5) with the number of molecular orbitals N. Unfortunately, when restricted Hartree-Fock orbitals are employed, the potential energy curves calculated with this method are of little use at large interatomic separations because of the diverg...

Full configuration interaction potential energy curves for breaking bonds to hydrogen: An assessment of single-reference correlation methods

Several approximate correlation methods have been assessed for bond breaking reactions in BH, HF, and CH4 by comparison to the full configuration interaction limit. Second-order Møller–Plesset perturbation theory, coupled-cluster singles and doubles ~CCSD!, coupled-cluster with perturbative triples @CCSD~T!#, and the hybrid density-functional method Becke three parameter Lee–Yang– Parr have bee...

Direct ab Initio Dynamics Studies of the Hydrogen Abstraction Reactions of Hydrogen Atom with Fluoromethanes

A direct ab initio dynamics study on the gas-phase reactions of atomic hydrogen with different fluoromethanes has been carried out. The thermal rate constants were calculated using canonical variational transition state (CVT) theory augmented by multidimensional semiclassical zero and small curvature tunneling approximations. The potential energy surfaces for the reactions were calculated using...

A transformed framework for multireference dynamic correlation

Multireference correlation remains a driving force for the development of new quantum chemical methods. There are now many methods to describe the correlation in the active spaces with up to 50 orbitals that produce a multireference wavefunction that is formally the sum of many determinants. The remaining challenge is to efficiently describe dynamic correlation outside of the active space. Dyna...

Second-order Moller-Plesset perturbation (MP2) theory at finite temperature: relation with Surjan's density matrix MP2 and its application to linear-scaling divide-and-conquer method