Multistate Complete-Active-Space Second-Order Perturbation Theory Based on Density Matrix Renormalization Group Reference States

A Local Complete Active Space 2nd-Order Perturbation Theory Method

Pyrazine excited states revisited using the extended multi-state complete active space second-order perturbation method.

We demonstrate that the recently developed extended multi-state complete active space second-order perturbation theory (XMS-CASPT2) [Shiozaki et al., J. Chem. Phys., 2011, 135, 081106] provides qualitatively correct potential energy surfaces for low-lying excited singlet states of pyrazine, while the potential energy surfaces of the standard MS-CASPT2 methods are ill-behaved near the crossing p...

Second-order perturbation theory with complete and restricted active space reference functions applied to oligomeric unsaturated hydrocarbons.

Multiconfigurational second-order perturbation theory based on either a complete active space reference wave function (CASSCF/CASPT2) or a restricted active space reference wave function (RASSCF/RASPT2) has been applied to compute one-electron ionization potentials and vertical electronic energy differences of oligomers of length n formed from ethylene (n = 1-10), acetylene (n = 1-5), and pheny...

Comment on “ Density - matrix renormalization - group method for excited states ”

In a recent paper (Phys. Rev. B 59, 9699 (1999)), Chandross and Hicks claim to present a new density matrix renormalisation group (DMRG) method for dealing with excited states of quantum lattice models. The proposed improvement to the DMRG—the inclusion of excited state wave functions in addition to the ground state in the density matrix when calculating excitations— is in fact standard pratice...

From density-matrix renormalization group to matrix product states

In this paper we give an introduction to the numerical density matrix renormalization group (DMRG) algorithm, from the perspective of the more general matrix product state (MPS) formulation. We cover in detail the differences between the original DMRG formulation and the MPS approach, demonstrating the additional flexibility that arises from constructing both the wavefunction and the Hamiltonia...