Elastic behaviors of a single three-dimensional compact chain adsorbed on the attractive surface are investigated using the pruned-enriched-Rosenbluth method (PERM).The size and shape of the chain

such as mean-square end-to-end distance R2

mean-square radii of gyration S2xy and S2z

and shape factor δ* are studied with different adsorption interaction energy and different positions of the chain on which the force is exerted.During the elasticity process

the shape factor δ* first decreases with the shape of chains in a sphere

then increases and the chain extends to be a rod shape along the direction of the force.It decreases again

and at the end it remains a constant value.If the chain is far away from the adsorbing surface

all of the conformational properties remain constant

and there would appear the “jump point”.On the other hand

some thermodynamic properties such as the average Helmholtz free energy per bond A

average energy per bond U/N

average attraction energy per bond Ua/N

average contact energy per bond UC/N

elastic force f and energy contribution to elastic force fU are also calculated during the elasticity process.Different thermodynamic behaviors are obtained when the force acts on different monomers of the chain.Obviously

there exist several long plateaus for elastic force f with strong adsorption interaction

which agrees well with experimental results.We also discuss elastic behaviors of compact chains with weak adsorption interaction

which cannot be obtained from experimental methods.