Path integral Monte Carlo (PIMC) method is employed to study the thermal properties of the X@C50 [X=H2,He,Ne,Ar] system at temperatures from 5 K to 300K.The interaction energies and probability distribution functions of one noble gas atom or H2 inside D5h-symmetry C50 are obtained.A rough sphere model is used in calculating interaction energies,as a comparison.This model gives much lower interaction energy than PIMC calculations on all X@C50,except He@C50.The PIMC method and the sphere model get nearly the same values of interaction energies on He@C50.The spatial distributions are enlarged by the increase in temperature,while the interaction energies change slowly in a wide range of temperature.Temperature is not the major reason for the stability of the system.It is impossible to trap an X atom into C50,except H2 because only the H2@C50 has positive interaction energies from the PIMC calculations.