Over the past decade we chemists have witnessed a tremendous increase in our capability
to carry out quantum chemical calculations of a size that could hardly have been imagined …

Since its introduction into quantum chemistry in the late 1960s by Cizek and Paldusf “3
coupled cluster theory has emerged as perhaps the most reliable, yet computationally …

Coupled cluster theory with single and double excitations accurately describes weak
electron correlation but is known to fail in cases of strong static correlation. Fascinatingly …

We describe an alternative procedure for obtaining approximate Brueckner orbitals in ab
initio electronic structure theory. Whereas approximate Brueckner orbitals have traditionally …

The equilibrium geometry, harmonic vibrational frequencies, and infrared transition
intensities of p-benzyne were calculated at the MBPT (2), SDQ-MBPT (4), CCSD, and CCSD …

Using a Lagrangian-based approach, we present a more elegant derivation of the equations
necessary for the variational optimization of the molecular orbitals (MOs) for the coupled …

Density functional theory (DFT) has been applied to three open-shell molecules (NO3, O4+,
and O2+) for which the unrestricted Hartree–Fock (UHF) wavefunction breaks spatial …

The effects of Hartree–Fock orbital instabilities on force constant predictions at both Hartree–
Fock and correlated levels of theory are investigated. Due to the quadratic dependence of …

Open-shell systems like free radicals, biradicals, or many transition metal complexes have
been very attractive fields for quantum chemical investigations for a long time and enjoy a …

Small carbon clusters (C n, n= 2− 15) are produced in a molecular beam by pulsed laser
vaporization and studied with vacuum ultraviolet (VUV) photoionization mass spectrometry …