The First-Principles Calculations Of The Effects Of Interactions On Thermal Transport In Two-Dimensional Materials

In recent years,two-dimensional materials have received extensive attention in various fields due to their excellent physical and chemical properties.More and more two-dimensional materials have been successfully prepared by experiments,and gradually moved to practical applications.As the size of novel electronic devices and equipment gradually develops to the micro/nanoscale,thermal management and energy conversion of them face the challenges.In particular,compared with micro/nanoscale and macro-scale thermal transport,physical phenomena and principles are quite different.The thermal transport problem of materials in nanoscale needs to be developed urgently.The outstanding thermal properties also make the two-dimensional materials as ideal heat dissipation materials,thermoelectric materials and thermal insulation materials in the future.Understanding the phonon thermal transport of two-dimensional materials plays an important role in designing new two-dimensional materials and developing applications of two-dimensional materials.Although many studies have reported the thermal properties and control methods for tuning the thermal properties of two-dimensional materials.However,at present,researchers have been devoted to studying single-layer two-dimensional materials,while ignoring the effects of layer numbers,substrate effect,and interlayer interaction forces on the thermal transport of two-dimensional materials.Therefore,there is a lack of research on the effect of interactions on thermal transport for two-dimensional materials.In this work,based on density functional theory,the first-principles calculations are used to solve the Boltzmann transport equation.We mainly studied the strain response of thermal conductivity of the monolayer and bilayer penta-graphene affected by the interlayer interaction force,the effects of interlayer interactions on bilayer graphene and graphite on thermal conductivity,the weak interaction force of two-dimensional materials and the interfacial thermal transport between the film and substrate:First,we studied the strain response of the thermal conductivity of monolayer and bilayer penta-graphene.We found that the monolayer and bilayer penta-graphene have a large difference in the variation of thermal conductivity under tension stress,that is,the thermal conductivity first increases and then decreases with the variation of tensile stress.However,the thermal conductivity of bilayer penta-graphene decreases more.The reason for the difference of the variation of thermal conductivity is that the interlayer interaction weakens the phonon relaxation time of some unique ultra-low frequency phonon modes of bilayer penta-graphene.Therefore,bilayer penta-graphene will have tremendous opportunities to be applied for two-dimensional nanoscale device and thermal management owing to its largely tunable thermal conductivity.Secondly,we deeply studied the effect of interlayer interaction on the thermal conductivity of bilayer graphene and graphite.By strengthening the interlayer interaction on bilayer graphene and graphite,the in-plane thermal conductivity of the bilayer graphene decreases.However,the in-plane thermal conductivity of graphite only changes a little,and the out-of-plane thermal conductivity of that increases enormously.The anharmonicity of the bilayer graphene is enhanced by the interlayer interaction force,thereby weakening its in-plane thermal conductivity.The interlayer interaction force also enhances the out-of-plane phonon group velocity of graphite,which makes the out-of-plane thermal conductivity of graphite increase largely.Therefore,the results show that the effect of the interlayer interactions on the thermal conductivity of the layered two-dimensional material cannot be ignored.Next,the thermal conductivity and thermoelectric properties of new two-dimensional triphosphides?InP₃,GaP₃,SbP₃,and SnP₃?with weak interaction force were studied.The systematic analysis of the electronic band structure,phonon dispersion,thermal properties,carrier mobility,thermoelectric properties,and so on,of the two-dimensional triphosphides shows that these types of new two-dimensional materials have ultra-low thermal conductivity,and high thermoelectric figure of merit?ZT value?.Therefore,the monolayer triphosphides have ideal application prospects in the fields of thermoelectricity.Finally,the interfacial thermal conductance between substrates and the cubic III-V boron compound BX?P,N,As,Sb?was studied.We found that the matching degree of phonon density of states between the interface materials,the atomic mass,the phonon angular frequency and spectral heat flux have effects on the interfacial thermal conductance.We reported theoretical methods to weaken the interface thermal resistance and provided an important theoretical basis for finding a feasible method to adjust the interface thermal conductance.