TY - JOUR

T1 - A RASSCF study of free base, magnesium and zinc porphyrins

T2 - accuracy versus efficiency

AU - Kerridge, Andrew

PY - 2013/2/14

Y1 - 2013/2/14

N2 - The restricted-active-space self-consistent-field methodology is successfully applied to the study of free base-and regular metalloporphyrins, the latter containing magnesium and zinc central ions. It is shown that inclusion of all excitations involving the Gouterman frontier orbitals in the RAS2 subspace results in a numerically stable approach, producing highly accurate results at a fraction of the computational cost of the complete-active-space self-consistent-field method, whereas increasing RAS2 beyond this size leads to only modest improvement. Topological and orbital analysis shows that the approach is also able to give a highly accurate description of the electronic wavefunction. Inclusion of the entire p-conjugated subsystem in the active space results in more accurate excitation energies and a reduction in the dependence on the exact form of the perturbational Hamiltonian used to include dynamic correlation. The larger active space also resolves a quantitative disagreement in results obtained with and without the inclusion of dynamic correlation.

AB - The restricted-active-space self-consistent-field methodology is successfully applied to the study of free base-and regular metalloporphyrins, the latter containing magnesium and zinc central ions. It is shown that inclusion of all excitations involving the Gouterman frontier orbitals in the RAS2 subspace results in a numerically stable approach, producing highly accurate results at a fraction of the computational cost of the complete-active-space self-consistent-field method, whereas increasing RAS2 beyond this size leads to only modest improvement. Topological and orbital analysis shows that the approach is also able to give a highly accurate description of the electronic wavefunction. Inclusion of the entire p-conjugated subsystem in the active space results in more accurate excitation energies and a reduction in the dependence on the exact form of the perturbational Hamiltonian used to include dynamic correlation. The larger active space also resolves a quantitative disagreement in results obtained with and without the inclusion of dynamic correlation.

KW - SENSITIZED SOLAR-CELLS

KW - ELECTRONIC-ABSORPTION-SPECTRUM

KW - DENSITY-FUNCTIONAL THEORY

KW - COUPLED CASPT2 CALCULATIONS

KW - ANO BASIS-SETS

KW - EXCITED-STATES

KW - PERTURBATION-THEORY

KW - WAVE-FUNCTIONS

KW - TIO2 FILMS

KW - ROW ATOMS

U2 - 10.1039/c2cp43982d

DO - 10.1039/c2cp43982d

M3 - Journal article

VL - 15

SP - 2197

EP - 2209

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 6

ER -