Parametric Nonorthogonal Tight-Binding Model version number 1 (NTBM1) with the set of parameters for H-C-N-O systems is presented. This model compares well with widely used semiempirical AM1 and PM3 models but contains less fitting parameters per atom. All NTBM1 parameters are derived based on a criterion of the best agreement between the calculated and experimental values of bond lengths, valence angles and binding energies for various H-C-N-O molecules. Parameters are currently available for hydrogen, carbon, nitrogen, oxygen atoms and corresponding interatomic interactions. The model has a good transferability and can be used for both relaxation of large molecular systems (e.g., proteins or covalent cluster complexes) and long-timescale molecular dynamics simulation (e.g., modeling of thermal decomposition processes).
The program package based on this model is available for download at no cost from here as an executable file for Windows operating system. Currently only structural relaxation for H-C-N-O compounds is available. After the manuscript publication the source Fortran code will be introduced and the program functionality will be extended.
We plan to support this on-line resource regularly and update the software periodically. We hope that the model presented will be useful to the specialists in quantum-chemistry modeling.