C. Sosa, J. Andzelm, B. C. Elkin, E. Wimmer, K. D. Dobbs, and D. A. Dixon, “A Local Density Functional Study of the Structure and Vibrational Frequencies of Molecular Transition-Metal Compounds,” J. Phys. Chem., 96 (1992) 6630-36. DOI: 10.1021/j100195a022