Study On The Elastic Properties And Thermoelectric Effects Of Two-dimensional Nano-film Materials

Since the discovery of graphene,it has proved that two-dimensional materials can exist stably at normal temperature,so more and more people pay attention to the study of the properties of two-dimensional materials in recent years.As the physical properties of materials,mechanical properties have important research value,and elastic properties,as an important property reflecting the mechanical properties of materials,have attracted extensive attention.Since the second industrial revolution,electric energy has become a necessary energy in our daily life.However,due to environmental pollution and rapid energy consumption in the process of industrialization,thermoelectric materials,as clean energy,have come into the public view.In recent years,some laboratories have been able to prepare calcium hydrobromide(Ca HBr)by melting hydride and anhydrous bromide or metal and bromide in 900? hydrogen environment,and some of its properties have been studied,but the theoretical research is few,especially for the monolecular calcium hydrobromide theory research is few.As a semiconductor with simple production method and low raw material price,zinc oxide has been increasingly popular,especially the layered zinc oxide with graphene-like plane and honeycomb shape that can be prepared from wurzite structure.Based on density functional theory and Boltzmann transport theory,the elastic and thermoelectric properties of monolayer calcium hydrobromide,monolayer zinc oxide and bilayer zinc oxide have been calculated.Firstly,through structural optimization of the three materials,their stable crystal structures were obtained.On this basis,their elastic constants are calculated and their mechanical stability is proved.The elastic limits of monolayer calcium hydrobromide and monolayer zinc oxide are obtained by means of biaxial tensile strain.Secondly,the phonon spectra of monolayer calcium hydrobromide,monolayer zinc oxide and two-layer zinc oxide were calculated by Phonopy software without virtual frequency,which proved their thermodynamic stability.On this basis,the lattice thermal conductivity of monolayer calcium hydrobromide and bilayer zinc oxide calculated by BTE and RTA methods was calculated by Sheng BTE software.Then,Boltz Trap software was used to calculate the electron transport properties of single-layer calcium hydrobromate,single-layer zinc oxide and two-layer zinc oxide.Finally,the thermoelectric properties of monolayer calcium hydrobromate,monolayer zinc oxide and two-layer zinc oxide are analyzed.