A DFT study of a model compound of vitamin D

Abstract A theoretical study of a model compound of vitamin D was carried out by means of DFT calculations. In particular, the B3LYP functional with the 6-31G ∗ basis set was used to perform the investigations. Five energy minima of the model compound were optimised in this work (one of them in a folded arrangement). The results of this study agree with our previous HF calculations on the same model compound (E. Martinez-Nunez, S. A. Vazquez, and R. A. Mosquera, J. Comp. Chem., 18, 1647 (1997)) and contrast markedly with semiempirical and force field calculations. However, a discrepancy between the HF and the present DFT geometries and relative energies appears for the folded conformation, demonstrating that for this conformation, correlation effects are important. For geometries, our results are found to be in good agreement with X-ray crystallographic data.