Reparameterization And Auxiliary Basis Sets For Improving B3LYP Accuracy

B3LYP method has become a popular tool for electronic structure calculations in recent years due to its favorable combination of low computational cost and good accuracy for calculating accurate molecular structures,frequencies,and energies.However,for more than a decade,it is known that B3LYP are not capable of accurately and reliably modeling noncovalent interaction energies.Noncovalent interactions are of particular importance in many areas of chemistry,biology,and material science.Because these interactions are often strongly influenced by correlation effects,it is necessary to use computationally expensive high-order wave function methods to describe them accurately.High-order wave function methods,such as MP2 and CCSD(T),can accurately represent these long-range forces and have been the gold standard for studying these complexes.However,due to the rapid increase in computational costs with system size,these calculations have been limited to studies of relatively small molecular complexes.Therefor,in this paper,we were based on B3LYP method to study the basis set and functional that can improve the accuracy of noncovalent interaction calculations.(1)To explore the basis set effects in B3LYP computations,first we calculated the interaction energies for 4 representative dimers using B3LYP combined with 6 basis sets.According to the results,we next constructed the auxiliary basis sets of 2,3,4ZaP for hydrogen and the first-row atoms C-F in B3LYP level.However,we found that the auxiliary basis sets failed to improve significantly the accuracy of B3LYP in noncovalent interaction calculations.(2)Refitting the three parameters P2,P3 and P5 of general form of density functionals P2EXHF+ P1(P4EXSlater+P3△EXnon-local)+ P6EClocal+P5△ECnon-local(where the Pi=P6=1.0,P2+P4=1.0)by calculating the interaction energies of complexes in S66 data base.The S66 set is divided into three categories:electrostatic dominated(hydrogen bonding,23 complexes),dispersion-dominated(23),and "mixed"(20).For electrostatic dominated,P2=0.4,P3=0.5,P5=1.0;for dispersion-dominated,P2=0.3,P3=0.05,P5=0.6;for mixed,P2=0.25,P3=0.25,P5=1.0.And with a root-mean-square error of 0.55,0.30 and 0.50 kcal/mol,respectively.