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Manuscript Title: The general atomic and molecular electronic structure system HONDO: version 7.0.
Authors: M. Dupuis, J.D. Watts, H.O. Villar, G.J.B. Hurst
Program title: HONDO VERSION 7.0
Catalogue identifier: ABFS_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 52(1989)415
Programming language: Fortran.
Computer: IBM-43X1, IBM-308X.
Operating system: VM/SP HPO4.2, VM/XA SF2, VM/XA SP1 AND MVS/XA.
RAM: 4000K words
Word size: 32
Peripherals: disc.
Keywords: Atomic physics, Molecular, Structure, Quantum Mechanical wavefunction, Energy, Gradient, Hessian, Basis set, Optimization, Saddle point, Path reaction, Force constants, Electronic properties, Hartree-fock, Self-consistent-field (scf), Configuration Interaction (ci), Perturbation theory.
Classification: 2.1, 16.1.

Nature of problem:
The program calculates electronic wavefunctions in the clamped nuclei approximation. N-electron wavefunctions are expanded in terms of configuration-state-functions (CSF) which are antisymmetrized products of one-electron orbitals. The one-electron orbitals are written as linear combinations of atomic orbitals (basis functions). In addition to the molecular energy, forces acting on atoms can be calculated for many wavefunctions. Efficient algorithms take advantage of the availability of these forces for the determination of equilibrium structures, transition state structures, reaction pathways, and vibrational spectra.

Solution method:
A common feature of all the wavefunction calculations possible with HONDO lies in the creation of a disk file (usually large, sometimes very large) of the electron repulsion integrals over basis functions. For the self-consistent-field wavefunctions, Fock operators are constructed which depend on the electron density which in turn is obtained by diagonalizing the Fock operators. The process is stopped when self- consistency is reached. For these wavefunctions, the Fock matrices are dense and of the order of up to 250. Calculations of wavefunctions which include many configuration-state-functions involve finding the few lowest eigenvalues and corresponding eigenvectors of a large but sparse and diagonally dominant matrix, by means of an iterative approach. Derivatives of the energy are calculated for all 3 * N nuclear coordinates at the same time.

The numberof atoms in a molecule is limited to 50, while the number of basis functions used to expand the molecular orbitals may not be greter than 255. The maximum number of CSF's used in the wavefunction expansion is 65536.

Running time:
From a few seconds to several hours.