For the first time, full ab initio periodic calculations on a Ti-chabazite with a very low content of Ti (Ti/Si = 1/11) were done. The simulated crystal is less computationally demanding and it is similar to the real titanosilicates microporous materials such as TS-1 or Ti-beta, where the Ti/Si is lower than 1/30, and hence it can be used as a model system. The geometric and energetic features of the interaction of Ti-CHA with NH3, H2O, H2CO, and CH3CN were studied, principally at the Hartree-Fock level. Bare Ti-CHA and its NH3, H2O, H2CO, and CH3CN complexes were fully optimized at Hartree-Fock level with an upgraded version of the CRYSTAL code [Chem. Phys. Lett. 348, 131 (2001)] and such optimized structures were employed to calculate BEc (binding energy corrected for the basis set superposition error) at the Hartree-Fock and B3-LYP levels. (C) 2003 American Institute of Physics.