The First-principles Study Of Two-dimensional System Thermodynamics And Its Heat Transport

Carbon nanotubes and graphene are all important constituents of the carbon species in the low-dimensional system,and their excellent thermal,mechanical,electrical and other properties have aroused great interest.Since the breakthrough of graphene,two-dimensional layered nanomaterials with similar structures have attracted more and more attention in many fields.Now,supercomputers,servers,etc.in the course of the operation produce a lot of heat,these heats is not only harmful to the information processing,but also to the ambient temperature.Due to the microelectronics scale has been developed to the nanometer level;the device can be a good operation depends largely on the thermal conductivity of the material.With the miniaturization of the device and the improvement of performance,the scale of electronic devices has entered the nanoscale;the performance of the material heat conduction has a higher demand.In contrast to the thermal transport in the macro-system,the unique properties of thermal transport in low-dimensional systems,such as graphene materials,have a high thermal conductivity,thermal conductivity and scale correlation of systems,and so on.Thermal properties and thermal transport research has become a very important area of condensed matter physics.In addition,with the miniaturization of the device and the improvement of performance,the scale of electronic devices has entered the nano-scale.The performance of the material heat conduction has a higher demand and how a variety of physical and chemical methods to modify low-dimensional materials.Thus regulate the various properties of the material has become an important frontier direction.The oxidation of two-dimensional graphene has an important effect on the oxidation of graphene and the properties of graphene.The main work of this thesis is as follows:1.the first-principles calculation method(Gaussian)is used to modify the chemical structure of the two-dimensional system graphene.By introducing Stone-Wales(SW)defects and adding chemical substituents hydroxyl(-OH)on the chemical reaction rate of two-dimensional graphene under different chemical structures and some changes in the internal energy changes before and after the reaction.We modified the structure of two-dimensional graphene by changing the structure of the two-dimensional graphene to change the relevant thermodynamics and chemical properties.2.Weusing the first princple method(Vasp、Phonopy、ShengBTE)to study the two-dimensional system of alpha graphyne thermodynamic properties.By calculating the force constant of the graphyne to calculate the thermal conductivity.In addition,the thermal conductivity of the phonon is analyzed by studying the parameters of its thermodynamics.Through the analysis of two-dimensional graphite alkyne,it is planned to study and calculate the same material with classical and quantum research methods.In this paper,we found that graphene containing SW defect bond could greatly improve the rate of chemical oxidation reaction.After the introduction of SW defect bond,we can change the distribution of electron cloud on the graphene sheet,and improve the chemical reaction electron transfer rate;In addition,the study found that the addition of hydroxyl substituents on the graphene plate could also significantly reduce the oxidation of the transition state energy barrier,improve the rate of reaction.What’s more,through the comparison of the size of the three kinds of hybrid bonds of the delta-type graphyne,we conclude that the chemical reaction of the carbon-carbon triple bond in the chemical reaction is the lowest,that is,the chemical bond type is most likely to be broken.Besides,we study the thermal conductivity of graphene,graphene oxide and graphyne,and we found that the thermal conductivity of graphene is the highest among the three materials,but after the introduction of epoxy groups,the thermal conductivity of graphene can significantly reduce.Moreover,compare to the three materials,the thermal conductivity of graphyne are relatively low.