Atomic integral driven second order polarization propagator calculations of the excitation spectra of naphthalene and anthracene

TY - JOUR

T1 - Atomic integral driven second order polarization propagator calculations of the excitation spectra of naphthalene and anthracene

AU - Bak, KL

AU - Koch, H.

AU - Oddershede, Jens

AU - Christiansen, Ove

AU - Sauer, Stephan P. A.

PY - 2000/3/1

Y1 - 2000/3/1

N2 - An atomic integral direct implementation of the second order polarization propagator approximation (SOPPA) for the calculation of electronic excitation energies and oscillator strengths is presented. The SOPPA equations are solved iteratively using an integral direct approach and, contrary to previous implementations, the new algorithm does not require two-electron integrals in the molecular orbital basis. The linear transformation of trial vectors are calculated directly from integrals in the atomic orbital basis. In addition, the eigenvalue solver is designed to work efficiently with only three trial vectors per eigenvalue. Both of these modifications dramatically reduce the amount of disk space required, thus, increasing the range of applicability of the SOPPA method. Calculations of the lowest singlet excitation energies and corresponding dipole oscillator strengths for naphthalene and anthracene employing basis sets of 238 and 329 atomic orbitals, respectively, are presented. The overall agreement of our results with experimental spectra is good. The differences between the vertical excitation energies calculated by SOPPA and the position of the maximum intensity peaks in the experimental spectra are within the range of +/- 0.35 eV with two exceptions, the 4 (1)A(g) state of naphthalene and anthracene where a 0.85 eV and 0.41 eV deviation is found, respectively. The relatively large discrepancy for this transition is due to large contributions from two-electron excitations which cannot accurately be described in SOPPA. For naphthalene we find additional excitations to Rydberg states of (1)A(u) and B-1(2u) symmetry as compared with previous calculations. (C) 2000 American Institute of Physics. [S0021- 9606(00)30908-4].

AB - An atomic integral direct implementation of the second order polarization propagator approximation (SOPPA) for the calculation of electronic excitation energies and oscillator strengths is presented. The SOPPA equations are solved iteratively using an integral direct approach and, contrary to previous implementations, the new algorithm does not require two-electron integrals in the molecular orbital basis. The linear transformation of trial vectors are calculated directly from integrals in the atomic orbital basis. In addition, the eigenvalue solver is designed to work efficiently with only three trial vectors per eigenvalue. Both of these modifications dramatically reduce the amount of disk space required, thus, increasing the range of applicability of the SOPPA method. Calculations of the lowest singlet excitation energies and corresponding dipole oscillator strengths for naphthalene and anthracene employing basis sets of 238 and 329 atomic orbitals, respectively, are presented. The overall agreement of our results with experimental spectra is good. The differences between the vertical excitation energies calculated by SOPPA and the position of the maximum intensity peaks in the experimental spectra are within the range of +/- 0.35 eV with two exceptions, the 4 (1)A(g) state of naphthalene and anthracene where a 0.85 eV and 0.41 eV deviation is found, respectively. The relatively large discrepancy for this transition is due to large contributions from two-electron excitations which cannot accurately be described in SOPPA. For naphthalene we find additional excitations to Rydberg states of (1)A(u) and B-1(2u) symmetry as compared with previous calculations. (C) 2000 American Institute of Physics. [S0021- 9606(00)30908-4].

KW - COUPLED-CLUSTER SINGLES

KW - DYNAMIC POLARIZABILITIES

KW - MOLECULAR CALCULATIONS

KW - ELECTRONIC-SPECTRUM

KW - WAVE-FUNCTIONS

KW - BASIS-SETS

KW - BENZENE

KW - STATES

KW - IMPLEMENTATION

KW - APPROXIMATION

M3 - Journal article

SN - 0021-9606

VL - 112

SP - 4173

EP - 4185

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

IS - 9

ER -