The structure and magnetism of graphone

Graphone is a half-hydrogenated graphene. The structure of graphone is illustrated as trigonal adsorption of hydrogen atoms on graphene at first. However, we found the trigonal adsorption is unstable. We present an illustration in detail to explain how a trigonal adsorption geometry evolves into a rectangular adsorption geometry. We check the change of magnetism during the evolution of geometry by evaluating the spin polarization of the intermediate geometries. We prove and clarify that the rectangular adsorption of hydrogen atoms on graphene is the most stable geometry of graphone and graphone is actually antiferromagnetic.Comment: 11 pages, 4 figure

Supervisory Efficiency and Collusion in a Multiple-Agent Hierarchy

We analyze a principal-supervisor-two-agent hierarchy with inefficient supervision. The su-pervisor may collects a wrong signal on each agent’s unobservable effort level. When reportingto the principal, the supervisor can collude with one or both agents to manipulate the signalin exchange for a bribe. In contract design, we identify a new trade-off between the loss fromsupervisor-agent collusion and the risk from inefficient supervision: Although allowing collu-sion makes shirking more attractive to the agents, it brings in a benefit because it can “correct”an incorrect negative signal when the agent has exerted effort. Such collusive supervision savesrisk premiums that the principal has to pay for incentive provision. We characterize the princi-pal’s optimal contract choice among no-supervision, collusion-proof, and collusive-supervisioncontracts. We show that the collusive-supervision contract dominates when the supervisory ef-ficiency is at an intermediate level