STRUCTURAL EVIDENCE FOR CHEMICAL CONTRIBUTIONS IN THE BONDING OF THE HEAVY RARE GASES ON A CLOSE-PACKED TRANSITION METAL SURFACE - XE AND KR ON RU (001)

摘要

We have determined the geometries of two ordered structures of Xe and Kr on Ru(001) by LEED-IV analysis, of the (root 3 x root 3)R30(0)-Xe and the close-packed (3 x 3)-Kr structures. The Xe atoms sit on-top, with unexpectedly short Xe-Ru distance. In the Kr structure the adatom layer locks into threefold sites and the other sites are variable; however, most Kr atoms sit close to on-top, and these possess the shortest Kr-Ru distances. We argue that these site selections and distance variations can be taken as evidence for a chemical contribution in rare gas-metal bonding, in addition to the Van der Waals attraction. Some consequences and difficulties of this concept are discussed. [References: 27]