Properties Of Beryllium Chalcogenide Semiconductors (Be-X,X=S,Se, And Te): First-principles Investigation

The 5G industry is driving the accelerated arrival of the information age and increasing technological requirements for the semiconductor industry.Beryllium chalcogenide(Be-X,X=S,Se,and Te)semiconductor compounds with wide band gap and strong stiffness are the most attractive semiconductor materials for improving the lifetime of diode optical compounds and as the most desirable semiconductor materials for blue spectrum light-emitting optoelectronic devices.Due to the strong toxicity of beryllium Be and its compounds,there are large risks in the experimental synthesis of the compounds and the experimental research process is slow.At present,first-principles calculations have become increasingly sophisticated and have yielded great accomplishments in the field of materials calculations.Therefore,we adopt the first-principles calculations in this paper to study the beryllium chalcogenide(Be-X,X=S,Se,and Te)semiconductor compounds,aiming to fully understand their properties and further reveal their great potential and development prospects in future semiconductor technology.In this thesis,structural phase transitions,mechanical properties,thermodynamic properties,and electronic structure properties of Be-X(X=S,Se,and Te)compounds have been calculated based on first-principles plane wave pseudopotentials and generalized gradient approximation(GGA)methods.After performing high-pressure phase transitions to study the energy-volume and enthalpy difference-pressure relationships of Be-X(X=S,Se,and Te)compounds,the ZB phase and high-pressure Ni As phase are determined to be their most stable structures.The phonon spectra and elastic constants also indicate that the ZB structure and Ni As structure are structurally and mechanically stable.In addition,the phase transition pressures of Be-X(X=S,Se,and Te)compounds from ZB phase to Ni As phase are58.615 GPa,41.363 GPa and 29.313 GPa,respectively.Noteworthy are the calculation of the the three-dimensional surface configuration of the directional elastic modulus and the sound velocity property revealed that both the elasticity and sound velocity of Be-X(X = S,Se,and Te)compounds exhibit anisotropic characteristics,which is the first comprehensive study of their mechanical properties.In addition,we reported for the first time the thermodynamic properties of the high-pressure Ni As structure of Be S compounds,such as Debye temperature and specific heat capacity,and found that the Ni As structure is usable in a wide temperature range and has no significant effect on its material properties.The electronic structure properties of ZB structure and Ni As structure were specifically analyzed with Be S compound as the representative.It is concluded that Be-X(X=S,Se and Te)compounds are all semiconductors in the ZB phase.As for the Ni As phase,Be Te compounds are metallic phases,Be S compounds and Be Se compounds are semiconducting phases.Finally,the theoretical prediction of the properties of Be-X(X=S,Se and Te)compounds in this thesis is desired to be a reference and guide for subsequent experimental studies.