Extension of MINDO/3-FORCES Method

The semi-empirical MINDO/3-FORCES method was applied by M. Shanshal et al. [1 – 3]. In this method the molecular energy, obtained with the MINDO/3 method suggested by Dewar et al. [4] was completely minimized with the Murtagh-Sargent minimization technique [5]. The derivative of the energy was calculated analytically with Pulay’s Force method [6]. The MINDO/3-FORCES method was used to reproduce the following ground state properties: Molecular geometries [1,7 – 10], heats of formation [1,7 – 10], dipole moments [7 – 9], ionization potentials [7 – 9], vibrational frequencies, and infrared absorption intensities [11 – 13]. On the other hand, the MINDO/3-FORCES method was restricted to the first and second row elements H, B, C, N, O, F [1]. In the present paper the MINDO/3-FORCES method is extended to the third row elements Si, P, S, Cl, and the validity of this method is examined for molecules containing S and Cl.