Mid-frequency wavefront errors can be of the most importance for some optical components, but they're not explicitly covered by corresponding international standards such as ISO 10110. The testing methods for the ...Mid-frequency wavefront errors can be of the most importance for some optical components, but they're not explicitly covered by corresponding international standards such as ISO 10110. The testing methods for the errors also have a lot of aspects to be improved. This paper gives an overview of the specifications especially of PSD. NIF, developed by America, and XMM, developed by Europe, have both discovered some new testing methods.展开更多
In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the gener...In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.展开更多
文摘Mid-frequency wavefront errors can be of the most importance for some optical components, but they're not explicitly covered by corresponding international standards such as ISO 10110. The testing methods for the errors also have a lot of aspects to be improved. This paper gives an overview of the specifications especially of PSD. NIF, developed by America, and XMM, developed by Europe, have both discovered some new testing methods.
文摘In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.
