Molecular Dynamics Simulation Of The Tensile Load Response And Irradiation Damage In Amorphous SiO₂

With the rapid development of the economy,the demand for energy is increasing.Compared with other energy,nuclear energy is regarded as the most competitive energy in this century,and it is also one of the best ways to solve the current energy problems.With the further research in fusion physics experiments,it has been found that a large number of high-energy rays will be released after the deuterium-tritium fusion reaction,which makes the operating environment of the optical components in the laser inertial confinement fusion device changed from a single the laser damage is transformed into the interaction of the laser and various types of radiation.Such a complex environment causes problems such as large-area shedding film in the actual operating environment for components with a high damage threshold.And as poor impact resistance and brittle fracture hinder its use as a structural material.At present,the research damage of amorphous silica is mainly focused on the component,the own defects of materials or the laser damage behavior induced by environmental pollution,so it is very necessary to study its fracture behavior and resistance radiation performance of amorphous SiO₂.In this paper,molecular dynamics method is used to simulate the uniaxial tensile load response and cascade collision process of amorphous SiO ₂.The effects of different strain rates on the fracture strength and failure strain of amorphous silica are discussed.The study found that as the strain rate increases,the stress-strain response increases,and there is an obvious transition from brittle to ductile in the sample.At a lower strain rate,strain aggregation corresponds to the stress concentration phenomenon,resulting in brittle rupture.At higher strain rates,strain is uniformly introduced and local damage is reduced.Larger bond extension and bond angle opening at high strain rates are beneficial to maintaining the matrix structure,providing additional energy dissipation,and promot ing an increase in elongation.Theα-cristobalite has been proven to be the most stable configuration of crystalline SiO₂at room temperature,and it is completely composed of six-membered rings.From a mechanical point of view,the larger the proportion of the six-membered ring under the same strain,the greater the stress value must be applied to break the sample,so the greater the fracture strength at the higher the strain rate.In addition,the defects generation and the structure evolution of amorphous silica under single and cumulative flux irradiation environments,as well as the effects on its mechanical properties are also studied.Different coordination structures were used to characterize the changes in the structure of amorphous silica before and after irradiation.It was found that although a lot of dissociated atoms were generated during the thermal peak stage,no new defect structure was introduced.The structure of the atomic arrangement before and after irradiation on average statistical difference is small,stress-strain curve comparison before and after irradiation also confirms this phenomenon.When the material is continuously irradiated,during the cumulative flux irradiation process,when the PKA energy is 0.5 ke V,all types of clusters tend to stabilize after 9 recoils;when the PKA energy is 5 ke V,all types of clusters tend to stabilize after 15 recoils.From the structure evolution,structure arrangement and stress-strain curve before and after irradiation of single cascade and overlap cascade,it can be seen that the disordered structure induced by amorphous materials after irradiation will be submerged by the original disordered structure system.It can also be said that compared with traditional materials,amorphous materials have stronger self-recovery ability and better radiation resistance.These results are expected to provide a basis for the interaction influences of laser and multiple transient radiations on the components properties degradation.