Dispersion Basis Sets For Accurate Calculations Of Intermolecular Interactions

Intermolecular interactions are very important research content in the fields of biology,physics,chemistry,etc.For example,in the structure-based computer-aided drug design method,the vital part is to study the interactions between the receptor and the ligand whichcan be simplified as the interactions between the small molecule and the surface of the binding pocket.Therefore,accurate and efficient calculation of the intermolecular interaction is the key to improve the accuracy and hit rate of drug design.Quantum chemistry is a tool for accurately calculating the intermolecular interaction energy.The basis functions used in quantum chemistry calculations are mainly Gaussian-type functions.In the past few decades,Gaussian-type functions have been continuously developed and can cover many elements in the periodic table of elements.Due to the incompleteness of the limited basis set,it can cause errors in the calculation of the intermolecular interaction energy.However,if a larger basis set is selectedto improve the calculation quality of the intermolecular interaction,it will increase the calculation cost and consume more computing resources.So the research content of this paper is to improve the calculation accuracy of intermolecular interactions without increasing the calculation cost by optimizing the dispersion basis function index of the basis set.（1）Optimizing the dispersion basis function index.This article selects the four elements hydrogen,carbon,nitrogen,and oxygen,which are the most common elements in the compounds studied in the biological and chemical fields.We calculated the intermolecular interaction energy at the level of HF/cc-p Vn Z,HF/aug-cc-p Vn Z,MP2/cc-p Vn Z,and MP2/aug-cc-p Vn Z（n=D,T,Q）and modified the dispersion basis function exponents of the four elements H,C,N,and O based on the basis set of cc-p Vn Z and aug-cc-p Vn Z（n=D,T,Q）.According to the calculation results of the intermolecular interaction energy at different distances,the basis function index was optimized,and the interaction energy calculated by the optimized basis set was significantly improved than the original basis set.（2）Fitting the formulas of the basis function index related to distance.Since the interaction energy between molecules is related to the distance between molecules,the optimized optimal basis function index and the distance between atoms are used as two variables,and then we fitted a series of univariate polynomial function formulas of the basis function index for H,C,N,and O using six basis sets.When the interatomic distance and the intermolecular distance change,the corresponding basis function index can be adjusted according to the formula.（3）Calculating the intermolecular interaction energy.This paper selected four common dimer molecules in biomolecules:H₂O-H₂O,Peptide-Me OH,C₆H₆-C₆H₆,and Pentane-Ac NH₂.According to the formula of the basis function index related to the distance between the molecules,the corresponding basis function indexes were determined and then we calculated the intermolecular interaction energy at MP2/cc-p Vn Z and MP2/aug-cc-p Vn Z（n=D,T,Q）levels.The results show that under the same basis set,most of the calculation results of the basis set are better than the calculation accuracy of the basis set before optimization.The optimized dispersion basis function index in this paper improves the calculation accuracy of the intermolecular interaction without increasing the calculation cost,the fitted formula also provides theoretical support for the subsequent calculation of the intermolecular interaction energy.