An aluminum alloy （Al-Zn-Mg-Cu） subjected to deep cryogenic treatment （DCT） was systematically investigated. The results show that a DCT-induced phase transformation varies the microstructures and affects the mech...An aluminum alloy （Al-Zn-Mg-Cu） subjected to deep cryogenic treatment （DCT） was systematically investigated. The results show that a DCT-induced phase transformation varies the microstructures and affects the mechanical properties of the Al alloy. Both Guinier-Preston （GP） zones and a metastableη′phase were observed by high-resolution transmission electron microscopy. The phenomenon of the second precipitation of the GP zones in samples subjected to DCT after being aged was observed. The viability of this phase transfor-mation was also demonstrated by first-principles calculations.展开更多
The hydrostatic-pressure-dependent mechanical stability and optoelectronic behavior of Zn_4B_6O_（13）（ZBO） are calculated using the exchange-correlation functional Perdew–Burke–Ernzerhof generalized gradient appr...The hydrostatic-pressure-dependent mechanical stability and optoelectronic behavior of Zn_4B_6O_（13）（ZBO） are calculated using the exchange-correlation functional Perdew–Burke–Ernzerhof generalized gradient approximation and the hybrid functional PBE0 based on density functional theory. The calculated and experimental unit cell volumes and Vickers hardness of ZBO at zero pressure agree well. ZBO is mechanically stable under the critical pressure of 52.98 GPa according to the generalized stability criteria. Furthermore, Young＇s modulus and Vickers hardness decrease with increasing hydrostatic pressure. The strength and type of ZBO bonds are investigated by population and electron density difference. The electronic structure at zero pressure reveals that ZBO is an indirect band gap semiconductor, and the calculated 5.62-e V bandgap coincides well with the 5.73-e V experimental value, highlighting the success of the hybrid functional PBE0 calculations of electronic properties. The band gap almost increases as a second-order polynomial of pressure, and the indirect nature does not change with the applied external pressure. The optical reflectivity and absorption coefficient show that ZBO is an excellent ultraviolet photodetector. Our calculation results suggest that the elastic and optical properties of ZBO are highly stable over a wide pressure range.展开更多
基金supported by the Fundamental Research Funds for Central Universities of China(No. XDJK2014C008)the National Natural Science Foundation of China(No.51171156)the Key Scientific and Technoogical Projects of Chongqing(Nos.CSTC2012GGYS5001 and CSTC2013JCYJYS5002)
文摘An aluminum alloy （Al-Zn-Mg-Cu） subjected to deep cryogenic treatment （DCT） was systematically investigated. The results show that a DCT-induced phase transformation varies the microstructures and affects the mechanical properties of the Al alloy. Both Guinier-Preston （GP） zones and a metastableη′phase were observed by high-resolution transmission electron microscopy. The phenomenon of the second precipitation of the GP zones in samples subjected to DCT after being aged was observed. The viability of this phase transfor-mation was also demonstrated by first-principles calculations.
基金Project supported by the National Natural Science Foundation of China(Grant No.51171156)
文摘The hydrostatic-pressure-dependent mechanical stability and optoelectronic behavior of Zn_4B_6O_（13）（ZBO） are calculated using the exchange-correlation functional Perdew–Burke–Ernzerhof generalized gradient approximation and the hybrid functional PBE0 based on density functional theory. The calculated and experimental unit cell volumes and Vickers hardness of ZBO at zero pressure agree well. ZBO is mechanically stable under the critical pressure of 52.98 GPa according to the generalized stability criteria. Furthermore, Young＇s modulus and Vickers hardness decrease with increasing hydrostatic pressure. The strength and type of ZBO bonds are investigated by population and electron density difference. The electronic structure at zero pressure reveals that ZBO is an indirect band gap semiconductor, and the calculated 5.62-e V bandgap coincides well with the 5.73-e V experimental value, highlighting the success of the hybrid functional PBE0 calculations of electronic properties. The band gap almost increases as a second-order polynomial of pressure, and the indirect nature does not change with the applied external pressure. The optical reflectivity and absorption coefficient show that ZBO is an excellent ultraviolet photodetector. Our calculation results suggest that the elastic and optical properties of ZBO are highly stable over a wide pressure range.
