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Probing the Basicity of Regular and Defect Sites of Alkaline Earth Metal Oxide Surfaces by BF 3 Adsorption: A Theoretical Analysis
Author(s) -
Di Valentin Cristiana,
Locati Corrado,
Pacchioni Gianfranco
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400006
Subject(s) - chemistry , adsorption , oxide , molecule , binding energy , desorption , alkaline earth metal , ionic bonding , inorganic chemistry , metal , alkali metal , ionization energy , ion , crystallography , computational chemistry , analytical chemistry (journal) , ionization , atomic physics , organic chemistry , physics
Abstract The basicity of regular and low‐coordinate (LC) sites (steps, edges and corners) at the surface of alkaline earths with NaCl structure (MgO, CaO, SrO, and BaO) has been investigated by using BF 3 as a probe molecule. BO and BF distances; OBF bond angles; BF asymmetric stretching frequencies; O, B and F 1s core‐level binding energies; and the interaction energy of adsorbed BF 3 were determined by means of DFT calculations on cluster models. These adsorption properties were compared with those of complexes of BF 3 with molecules with various basicities (water, ammonia, phosphine, etc.). We show that many properties of adsorbed BF 3 , and in particular the experimentally accessible shifts in vibrational frequency, in B and F 1s core levels, and in BF 3 desorption temperature, exhibit a linear correlation with the surface basicity as measured by the vertical ionization potential of the oxide anions. On the other hand, shifts of the O 1s core level binding energy do not provide a simple way to detect surface basicity. On a given oxide surface, the differeing basicities of various sites result in measurable differences in adsorption properties. This suggests the potential use of BF 3 as a probe molecule for titrating LC sites on the surface of ionic oxides.