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Manuscript Title: Fortran 90 implementation of the Hartree-Fock approach within the CNDO/2 and INDO models
Authors: Sridhar Sahu, Alok Shukla
Program title: cindo.x
Catalogue identifier: AECN_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 180(2009)724
Programming language: Fortran 90.
Computer: PC's/Linux, Program has been tested with Intel Fortran Compiler (noncommercial version 10.1) and gfortran compiler (gcc version 4.3.0) with optimization option -O.
Operating system: Linux, Code was developed and tested on various recent versions of Fedora including Fedora 9 (kernel version 2.6.25-14).
Keywords: Hartree-Fock method, self-consistent field approach, CNDO/INDO models, Molecular orbitals.
PACS: 31.15.bu, 31.15.-p. 31.15.xr, 31.10.+z.
Classification: 16.1.

External routines: This program needs to link with LAPACK/BLAS libraries compiled with the same compiler as the program. For the Intel Fortran Compiler we used the ACML library version 3.6.0, while for gfortran compiler we used the libraries supplied with the Fedora distribution.

Nature of problem:
A good starting description of the electronic structure of extended many-electron systems such as molecules, clusters, and polymers, can be obtained using the Hartree-Fock (HF) method. Solution of HF equations within a fully ab initio formalism for large systems, however, is computationally quite expensive. For such systems, semi-empirical methods such as CNDO and INDO proposed by Pople and collaborators are quite attractive. The present program can solve the HF equations for both open- and closed-shell systems containing first- and second-row atoms using either the INDO model or the CNDO model.

Solution method:
The single-particle HF orbitals are expressed as linear combinations of the Slater-type orbital (STO) basis set specified by Pople and coworkers. Then using the parameters prescribed for the CNDO/INDO methods, the HF integro-differential equations are transformed into a matrix eigenvalue problem. Thereby, its solutions are obtained in a self-consistent manner, using methods of computational linear algebra.

Running time:
The examples provided each only take a few seconds to run. For a large molecule of cluster, however, the run time may be a few minutes.