SIZE DEPENDENCE OF MOBILITY ON THE SURFACE OF METAL-CLUSTERS - AMMONIA ON AG-10 AND AG-16

Citation
L. Lian et al., SIZE DEPENDENCE OF MOBILITY ON THE SURFACE OF METAL-CLUSTERS - AMMONIA ON AG-10 AND AG-16, The Journal of chemical physics, 104(13), 1996, pp. 5338-5344
Citations number
31
Categorie Soggetti
Physics, Atomic, Molecular & Chemical
ISSN journal
00219606
Volume
104
Issue
13
Year of publication
1996
Pages
5338 - 5344
Database
ISI
SICI code
0021-9606(1996)104:13<5338:SDOMOT>2.0.ZU;2-K
Abstract
Equilibrium constants for the reactions of NH3 with the silver cluster s, Ag-10 and Ag-16, have been measured in the gas phase as a function of temperature using a cluster flow reactor. The binding enthalpies, D elta H(300)degrees = -9.8 +/- 1.0 and -15.9 +/- 1.0 kcal mol(-1), and entropies, Delta S(300)degrees = -10.3 +/- 3.0 and -23.5 +/- 3.0 cal m ol(-1) K-1, have been obtained for the complexes Ag10NH3 and Ag16NH3, respectively. Statistical mechanics modeling indicates that NH3 is mob ile on the surface of Ag10NH3. In contrast, it is locally bound on Ag- 16. The implication is that the binding mechanism involves only electr ostatic interaction on Ag-10 and that Ag-16 provides a site favorable to a stronger classical chemical lone-pair bond. Thus ammonia may diff use on Aglo and be localized on Ag-16. (C) 1996 American Institute of Physics.