DYNAMICAL LOW ENERGY ELECTRON DIFFRACTION ANALYSIS FOR Cs/GRAPHITE(0001)-(√3X√3 ) R30°SURFACE

A model incorporating (Cs-A-ABAB) stacking with Cs atoms chemisorbed in hollow sites 2.70A above the top graphite plane and the two top graphite layers shear-shifted to AA stacking and expanded to a separation of 3.85A is the most reliable structure for Cs/graphite( 0001)- (√3 X√3) surfaces. The coexisting diffraction pattern including the diffraction ring and another set of (√3 X√3 ) diffraction pattern which has a 30°rotation angle with respect to the normal (√3 X√3 ) R30°diffraction pattern could be explained. We consider.this structure to be in a pre-intercalation state.