Dewar90 M. J. S. Dewar and Y.-C. Yuan, “AM1 parameters for sulfur,” Inorganic Chem., 29 (1990) 3881-90. DOI: 10.1021/ic00344a045 Related Articles: ReferencesSemi-Empirical MethodsDescribes the semi-empirical methods available in Gaussian: AM1, PM3, PM6, PM7.