We present ab initio Hartree-Fock lattice calculations on a series of heterocyclic and other compounds. Some of these have previously been studied by cluster calculations with the same D Z basis sets at the SCF level. The electric field gradients at the nitrogen centres, are related to NQR experimental determinations of nuclear quadrupole coupling constants. The compounds studied include imidaz...

Based on the corrected Hohenberg-Kohn-Sham total energy density functional [Y. A. Zhang and Y. A. Wang, J. Chem. Phys. 130, 144116 (2009)], we have developed two linear-expansion shooting techniques (LIST)- direct LIST (LISTd) and indirect LIST (LISTi), to accelerate the convergence of self-consistent field (SCF) calculations. Case studies show that overall LISTi is the most robust and efficien...

We first provide existence and uniqueness conditions for the solvability of an algebraic eigenvalue problem with eigenvector nonlinearity. We then present a local and global convergence analysis for a self-consistent field (SCF) iteration for solving the problem. The well-known sin Θ theorem in the perturbation theory of Hermitian matrices plays a central role. The near-optimality of the local ...

This paper presents an analytical derivation of a multiconfigurational self-consistent-field ~MC-SCF! solution of the time-independent Schrödinger equation for nuclear motion ~i.e. vibrational modes!. This variational MC-SCF method is designed for the mixed quantum/classical molecular dynamics simulation of multiple proton transfer reactions, where the transferring protons are treated quantum m...

1 Electronic Structure Calculations All electronic structure calculations were carried out with the ORCA program1. Density functional theory calculations on the BP862–6 (methanol and the tripeptide) and BLYP2–4,7 (only tripeptide) level of theory were performed using the def2-SVP basis8 set and the RI approximation with the def2-SVP/J auxilary basis set.9,10 B2PLYP11 computations (n-alkanes) us...

Different types of Gaussian basis sets for accurate LCAO calculations are discussed. For calculations designed to recover a substantial portion of the correlation energy, we suggest the use of basis sets comprising natural orbitals from correlated calculations on the atoms. These basis sets have proven to be very efficient in accounting for large fractions of the molecular correlation energy. F...