Theoretical Studies On Structural Prediction And Confined Interception Of New CON Polymeric Materials Under High Pressure

Light element C,O and N polymeric materials have the advantages of high energy density and environmental protection.Exploring the polymeric structure of pressure-induced light element formation is important for understanding light element molecular polymers and exploring a new generation of high energy density materials.A typical nitrogen molecule polymerisation forms a polymeric nitrogen material with an energy density more than three times that of a conventional high energy density material,TNT.Studies have shown that the dissociation of nitrogen molecules to form polymerised nitrogen structures only occurs under pressure conditions above 100 GPa and cannot be preserved to ambient conditions（stable above 42 GPa）,with extreme synthesis conditions and poor kinetic stability greatly limiting their application.The polymerisation of CO,which has a similar electronic structure to that of nitrogen molecules,is also capable of forming high energy density materials.In contrast,the CO polymerisation structure has a lower synthesis pressure and higher stability,but its energy density is much lower than that of the polymerised nitrogen structure.Therefore,the combination of the two results in a CON-polymerised structure that retains the high energy density properties of the polymerised nitrogen structure,while improving the synthesis conditions and stability of the structure.According to current reports,the CON polymeric structure contains N-N and C-O single bonds with high bonding energy,which release large amounts of energy during the bonding decomposition process,making it a potential high energy density material.In addition,the covalent network structure formed by the lighter elements C,O and N facilitates the formation of superhard materials.Consequently,CON polymeric materials have triggered a boom in their research.The current research on CON polymeric structures is mainly focused on structures with low nitrogen content,with fewer reports on nitrogen-rich polymeric structures.In contrast,nitrogen-rich structures tend to have higher energy density and mechanical hardness.Therefore,in this thesis,a study of nitrogen-rich CON polymerisation structures was carried out to explore polymerisation structures with excellent stability,high energy density properties and good mechanical properties.At the same time,a study on the ambient temperature and atmospheric pressure interception of CON polymerisation structures was carried out using a template domain-limited approach.1.Structure prediction and property study of new CON polymeric materials under high pressureCrystal structure predictions for different ratios of（CO）x Ny were carried out at50,100 and 150 GPa.Two high-pressure stable phases（Cm-C₂O₂N and Pbam-CON）and four substable phases(P-3m1-C₃O₃N,Cmca-CON₂,Cm2m-CON₄and Cm-CON₆)were obtained.Of these,Cm-C₂O₂N,Pbam-CON and Cmca-CON₂are kinetically stable at atmospheric conditions.Bonding analysis indicates that the formation of C-N bonds in the structures is key to structural stability and acts as a limit to the decomposition of the high energy-bearing C-O and N-N bonds.Furthermore,the Vickers hardnesses of the Cm-C₂O₂N,Pbam-CON and Cmca-CON₂structures are35.12,47.73 and 38.85 GPa,respectively,making them potential superhard materials.The two higher nitrogen-containing Cm2m-CON₄and Cm-CON₆structures have energy densities of 7.53 and 8.14 k J/g respectively,much higher than the conventional high-energy density material TNT（4.3 k J/g）and are potential high-energy density materials.The proposed new superhard and energy-containing materials extend the research field of the CON system and provide a theoretical reference for exploring new high-energy-density,superhard materials.2.Theoretical study of the domain-limited layered C₃O₃N structureA theoretical study of the domain-limited layered C₃O₃N structure has been carried out using graphene as the domain-limited template using the first principles approach.The stability of the polymeric structure of C₃O₃N in the domain-limited template and its bonding mechanism have been systematically investigated through crystal structure chirality,molecular dynamics calculations and electronic property calculations.The results of molecular dynamics simulations show that the C₃O₃N domain-limited system in graphene can be stabilized to ambient conditions,which enables the interception of the C₃O₃N polymeric structure at ambient temperature and pressure.Electronic property calculations show that the physical mechanism by which the domain-limited template stabilises C₃O₃N at ambient pressure is the charge transfer effect of both.This work is the first to intercept the atmospheric pressure unstable CON polymerization structure to ambient conditions by the domain-limited method,which provides a new research idea for the interception of CON structures at ambient temperature and pressure conditions.