In this paper

based on the density functional(B3LYP) method with Relativistic Effective Core Potential(RECP)

the structures of UD3 and UT3 molecules are optimized.The results show that the ground state of UD3 and UT3 molecules are 4A1

with a disassociation energy of 9.112 eV

which belongs to the C3V symmetry.The standard formed thermodynamic functions for UD3 and UT3 molecules are worked out by thermodynamic method.The calculation results show that UD3 and UT3 molecules have thermodynamic stability under 798.15 K and 698.15 K

respectively.