Siting of B, Al, Ga or Zn and bridging hydroxyl groups in mordenite: an abinitio study

The siting of B, Al, Ga or Zn and bridging OH groups in the framework of mo rdenite was studied by ab initio Hartree-Fock MO methods. The basis set eff ect on the calculation results was investigated in details. It was shown th at heteroatoms including B, Al, Ga and Zn prefer the same T sites, T-3 and T-4, when replacing Si in mordenite framework. The presence of the charge-b alancing protons does not influence the siting sites of heteroatoms, but st abilizes the structure of the substituted clusters. For the two preferred s ubstitution sites T3 and T4, the charge-compensating protons prefer to atta ch to O-9 and O-10, respectively, in case of B, Al or Ga substitution. For Zn substitution at T3 or T4 site, the two charge-compensating protons favor bonding with O-9 and O-1 or O-10 and O-2, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.