I am calculating elastic properties but the functional used (PBE-GGA) is not giving so close values. is there any other ex/corr functional other than PBE-GGA which gives better result for structural and elastic properties?
you can try with PBEsol. PBEsol is intended to improve on PBE for equilibrium properties such as bond lengths and lattice parameters. See Phys. Rev. Lett. 100, 136406 (2008)