Study On Structural Changes And Properties Of Organic Materials Under High Pressure

With the increasing application of organic materials in electronic devices,it has increasingly become a research hotspot in materials science.Especially for the study of electromagnetic properties and optical properties,it provides theoretical support for its application in new electronic devices.The structure of organic materials is weak due to intermolecular interactions,often unstable under extreme conditions,and prone to property changes.Therefore,under pressure,it is of great significance to study its structural changes and properties.First,the research progress of high-pressure phase transition of organic materials,density functional theory of materials and simulation calculation methods are introduced.Through the reported research of many materials under high pressure conditions,we have successfully summarized the first-principles calculation method based on density functional theory to study the structure and properties of organic materials.Secondly,the organic material 1-2-Isopenteny(foreign alkenyl purine)is modeled and calculated to study the structure under high pressure.In the range of 0～300 GPa,the changing trends of parameters such as lattice constant,unit cell volume,bond length and bond angle under different pressures are analyzed.Studies have shown that the molecular structure of materials will undergo complex changes under high pressure conditions: p<140GPa,the lattice constant a slowly decreases with increasing pressure,and when p>140GPa,a basically does not change with increasing pressure except Two troughs at 150 GPa and 200 GPa and a sharp peak at 260 GPa.The lattice constant b decreases with increasing pressure at p<190Gpa,except for peaks at 150GPa;p>200GPa increases with increasing pressure and peaks at 250 GPa.The lattice constant c is at p<220GPa,which decreases with increasing pressure,and a peak appears at 200 GPa.p>200GPa increases with pressure,p>280GPa basically does not change.The β angle increases with the increase of pressure,p<220GPa increases slowly,then increases rapidly,and after p>260GPa it tends to be stable.Combining these transformations,we can speculate that 1-2-Isopenteny undergoes structural phase transformation under certain pressures.Then from the aspects of electronic structure,density of states and optical properties,the properties of the material under the pressure were studied.In the analysis of band gap and state density,p<100GPa,the band gap decreases with increasing pressure;100～190GPa,the band gap decreases slowly,except for the trough of 150 GPa.The bandgap change ratio is steeper afterp>200GPa,and the bandgap drops to zero at 210,220,240,260,and 270 GPa,so it can be speculated that the phase change experienced is: insulator→semiconductor→metal phase,which is different from the previous structural change Match.On the other hand,according to the absorption spectrum,there are three strong absorption peaks at 150 GPa,and then the main peak shifts to high energy as the pressure increases,indicating that high pressure affects its optical activity and stability,which has certain reference significance for the research of electronic devices under high pressure environment..Finally,the structural changes and properties of IBO(acetamide oxime)organic materials under high pressure were studied,and the pressure range of 0～300GPa was completed.IBO cell modeling,crystal structure analysis and partial property analysis were completed.In the study of the unit cell structure,it is found that the three axial directions(a,b,c)of 0～70GPa all decrease with the increase of pressure,and the a-axis decreases greatly.Then in the range of 80～100GPa,the a axis increases,while the b and c axes decrease,indicating the difference in the dimensions of the material.In the range of 100～250GPa,the a-axis occurs at 120 GPa,150GPa,and 180 GPa,which is relatively large and small.Combined with the β changes under these pressures,it is speculated that the structural changes of IBO cause the properties to change.This paper studies the effect of high pressure on the structure and properties of organic materials.Mainly from the aspects of unit cell structure,electronic properties and optical properties,the internal relationship between material structure and properties was discussed,and the effective regulation of pressure on the structure and properties of organic materials was verified.