A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified Becke–Johnson(mBJ)potential approximation,is used to investigate the electronic band s...A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified Becke–Johnson(mBJ)potential approximation,is used to investigate the electronic band structure and optical properties of spinel oxides:GeZn_(2)O_(4).The predicted band gaps using the mBJ approximation are significantly more accurate than the proposed previous theoretical work using the common LDA and GGA.Band gap dependent optical parameters,like the dielectric constant,index of refraction,reflectivity and optical conductivity are calculated and analyzed.The results from the dielectric constant shows that the numerical value of the static dielectric,after dropping constantly,becomes less than zero and the material exhibits metallic behavior.The refractive index also drops below unity for photons higher than 18 eV,which indicates that the velocities of incident photons are greater than the velocity of light.However,these phenomena can be explained by the fact that a signal must be transmitted as a wave packet rather than a monochromatic wave.This comprehensive theoretical study of the optoelectronic properties predicts that these materials can effectively be used in optical devices.展开更多
We investigate half metallicity in a chromium(Cr)-substituted AlN dilute magnetic semiconductor using the full-potential linearized augmented plane-wave method.Our results show that Al_(0.75)Cr_(0.25)N is half metal a...We investigate half metallicity in a chromium(Cr)-substituted AlN dilute magnetic semiconductor using the full-potential linearized augmented plane-wave method.Our results show that Al_(0.75)Cr_(0.25)N is half metal and holds a net integer magnetic moment of 3μβwith lattice compression.The half−metallic nature is maintained from the relaxed lattice constant 4.36Åto 4.09Å.An abrupt change of the physical properties is observed at a robust transition lattice constant of 4.09Å,and the material transforms from half metal to metal.We find that up to 6%compression,the material maintains its half-metallic nature.Furthermore,we also confirm that the origin of ferromagnetism in Al_(0.75)Cr_(0.25)N is double exchange.展开更多
文摘A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified Becke–Johnson(mBJ)potential approximation,is used to investigate the electronic band structure and optical properties of spinel oxides:GeZn_(2)O_(4).The predicted band gaps using the mBJ approximation are significantly more accurate than the proposed previous theoretical work using the common LDA and GGA.Band gap dependent optical parameters,like the dielectric constant,index of refraction,reflectivity and optical conductivity are calculated and analyzed.The results from the dielectric constant shows that the numerical value of the static dielectric,after dropping constantly,becomes less than zero and the material exhibits metallic behavior.The refractive index also drops below unity for photons higher than 18 eV,which indicates that the velocities of incident photons are greater than the velocity of light.However,these phenomena can be explained by the fact that a signal must be transmitted as a wave packet rather than a monochromatic wave.This comprehensive theoretical study of the optoelectronic properties predicts that these materials can effectively be used in optical devices.
文摘We investigate half metallicity in a chromium(Cr)-substituted AlN dilute magnetic semiconductor using the full-potential linearized augmented plane-wave method.Our results show that Al_(0.75)Cr_(0.25)N is half metal and holds a net integer magnetic moment of 3μβwith lattice compression.The half−metallic nature is maintained from the relaxed lattice constant 4.36Åto 4.09Å.An abrupt change of the physical properties is observed at a robust transition lattice constant of 4.09Å,and the material transforms from half metal to metal.We find that up to 6%compression,the material maintains its half-metallic nature.Furthermore,we also confirm that the origin of ferromagnetism in Al_(0.75)Cr_(0.25)N is double exchange.
