High-throughput Design And Screening Of Superhard Carbon With Zeolitic Topologies

The hardness of superhard materials is much higher than that of other materials.So,superhard materials plays an important role in industry.Superhard materials mainly include diamond and cubic boron nitride.However,diamond has its own disadvantages,such as easy oxidation and its affinity with iron group elements,which limits its industrial application.The hardness of cubic boron nitride is only 2/3 that of diamond.Therefore,people are eager to design new materials with higher hardness and better properties than the existing superhard materials.With the development of computer computing ability,a series of sp³hybrid carbon structures have been predicted in recent years,which provides targeted structures for the experimental synthesis of superhard carbon.However,the prediction of traditional carbon structure is often limited to specific topology,and the number of designed structures is small.In addition,most of the traditional methods aim at building the structure with the minimum energy,so the performance of the structures can’t be predicted in advance,and the design efficiency of superhard structure is low.The framework of zeolite structures is composed of TO₄ tetrahedrons with shared vertices,which is three-dimensional and four-connected structure.It is very similar to the structure of sp³ hybrid carbon in topology.Many theoretical or experimental reports of superhard carbon structures have the same topology as zeolite structures.With the development of computer technology,zeolite structures has been predicted for several decades,and abundant topological data have been accumulated.In this paper,based on the known zeolite topology,a property-oriented structural design method is proposed.Firstly,starting from the topological structure of zeolites,the structural design strategy of"first screening,then replacement,and then screening"is adopted to transform the zeolite structure into sp³ hypothetical carbon structure by element replacement and changing the unit cell,so as to realize the high-throughput prediction and screening of superhard carbon structure.This paper consists of two parts.In the first part of,106 known superhard carbon structures were collected for data integration and analysis,and the common structural features of these structures were extracted as the criteria for subsequent structural screening.In order to reduce the calculation amount,we adopted the strategy of"screening first,then replacing and then screening".In the topological stage of zeolites,according to the framework density and rings,25867 molecular sieve structures were screened out from 630,127 zeolite structures,and these structures were transformed into hypothetical carbon structures through element substitution.On this basis,molecular mechanics optimization calculation and quantum mechanics optimization calculation were carried out for the obtained carbon structure,and the rationality of the designed carbon structure was tested with energy as the benchmark.Finally,675 hypothetical carbon structures were got.Among them,674 carbon structures meet the standard of superhard structure.In the second part,we selected four ultrahard carbon allotrophes:073fffff21134,073ffff22479,073cefff21023 and 073cefff22054 for calcuiation.They come from Ibca,Ibca,Ibca,and Cmma space group respectively,which are composed of 5-,6-,8-membered rings.After calculation and analysis the energy,phonon spectra and elastic constants of these four structures,the thermodynamic stability,dynamic stability and mechanical stability of these hypothetical ultrahard carbon structures are verified.We also calculated the electronic and mechanical properties of these four structures.The proposed structure design method based on zeolitic topology has not only high-throughput designed hundreds of superhard carbon structures,but also got four ultrahard carbon structures with good properties and stability,which provides a new idea for the high-throughput design of superhard carbon structures.