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Scaled quantum mechanical force field for Peroxyacetyl Nitrate (PAN) A. C. Coronel a, L. E. Fernández b and E. L. Varetti c a Instituto de Química Orgánica, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, 4000 S.M. de Tucumán, Argentina. b Instituto de Química Física, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Lorenzo 456, 4000 S.M. de Tucumán, Argentina. c Centro de Química Inorgánica (CEQUINOR, CONICET-UNLP), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.Correo 962, 1900 La Plata, Argentina. Optimized structure and vibrational frequencies were obtained for peroxyacetyl nitrate (PAN) by means of density functional theory (DFT) methods. The calculations were made with the Gaussian 03 set of programs [1]. The existing experimental data and assignments for PAN were confirmed by the theoretical results. Such quantum chemistry calculations were performed in order to obtain the force constants of the mentioned molecule, which were subsequently scaled to reproduce the experimental frequencies. Such adjustment was made using the formalism of the Scaled Quantum Mechanics (SQM) force field, as defined by Pulay et al. [2], in which the diagonal force constants are multiplied by scale factors fi , fj ,... and the corresponding interaction constants are multiplied by (fi . fj )1/2 , adjusting the scale factors to reproduce as well as possible the experimental frequencies. The SQM force field was used to calculate the potential energy distribution, which represents the contribution of each main force constants to the different modes of vibration, and the internal force constants as a characteristic parameter of each chemical bond. References [1] Frisch M. J. et al. Program Gaussian 03, Revision A.1; Gaussian, Inc., Pittsburgh PA, U.S.A., 2003. [2] Pulay P., Fogarasi G., Pongor G., Boggs J. E., Vargha A., J. Am. Chem. Soc. 1983, 105, 7037-7047.