A theoretical study of the Al-(SiO)_1,2 compounds

摘要

Density-functional theory and ab initio methods have been applied to characterize the structural features of Al-(SiO)_1,2 compounds.According with previous work [Schnockel et al.,J.Chem.Phys.112,1444 (2000)],it has been shown that an Al atom spontaneously reacts with SiO forming a linear O-bonded molecule,AlOSi (~2II).Three minima have been found in the potential-energy surface of Al-(SiO)_2:two local minima corresponding to cis-cis and to trans-trans forms with two equivalent SiO fragments arising from addition of a second SiO to AlOSi,and the third one corresponding to the global minimum with a chain structure.It has been shown that the chain structure could bve obtained either spontaneously from the reaction btween an aluminum atom and a cyclic (SiO)_2 dimer or from the isomerizatioin reaction of the cis-cis Al-(SiO)_2 structure but requiring,in this case,an activation energy about 10 kcal/mol.Bonding characterization performed within topological frameworks reveals that the interaction in all the (SiO)_n and Al-(SiO)_n (n=1 and 2) compounds should be considered as a highly polar interaction.Structural comparisons have been made between Al-dicarbonyl and Al-disilonyl on the ground of the topological analysis.