Application Of Revised Van Der Waals Functionals In The DFT Simulation Of Energetic Materials

Energetic materials are a kind of materials with a long history.Energetic materials have played an important role in the development of human civilisation.Nowadays,there is still a strong need for the development of new energetic materials,serving as explosives and propellants in areas such as defence and aerospace.Due to the special properties of energetic materials,computational simulation is an important tool in the research.While density functional theory has been widely used in material science as a first-principle method,which balances computational efficiency and accuracy,the simulation of energetic materials encounters the dilemma that the commonly-used methods cannot accurately describe the intermolecular interactions,because density functional theory methods cannot describe the van der Waals interaction.The aim of this paper is to evaluate the existing methods which correct the van der Waals interaction based on density functional theory.Apart from this,we aim to improve an existing method and use the method in the study of energetic materials.In order to assess the accuracy of current van der Waals functionals within the framework of density functional theory,this paper first tests two methods which are mostly used in the calculation of van der Waals interaction:SCAN+rVV10 and PBE+D3 medthod.Three weak interactions systems representing van der Waals interaction,hydrogen bonding and π-bond stacking,respectively,are constructed from small molecules containing H,C,N and 0.The benchmark potential energy curves calculated by the MP2+ΔCCSD(T)method were used to evaluate the SCAN+rVV10 and PBE+D3 methods.The results show that both methods can achieve chemical accuracy.However,SCAN+rVV10 method has an advantage in reproducing the details of the potential energy curves,while PBE+D3 has a clear advantage in terms of computational efficiency.In addition,both methods have large errors in the calculation of van der Waals interaction when the distance between the dimer is smaller than the equilibrium distance,which provides a direction for further development of van der Waals funtionals in the future.Next,this paper improves the local atomic potential(LAP)method by proposing a new potential function form and add this potential on the PBE functionals.The new function form ensures the van der Waals interaction satisfy the 1/r6 asymptotic behaviour.The new potential function parameters are obtained by fitting the benchmark potential curves calculated by MP2+ΔCCSD(T)method.The PBE+LAP method is applied to calculate the density,elastic modulus,polymorphism and other properties of energetic materials.The results show that the PBE+LAP method is more accurate than the PBE+D3 method in calculating density and elastic modulus.When comparing the thermal stability of polymorphic energetic materials,the PBE+LAP method can accurately predict the stability in most cases.