The lattice dynamic, elastic, and thermodynamic properties of Be Se were investigated with first principles calculations. The phase transition pressure from the zinc blende（B3） to the nickel arsenide（B8） structure...The lattice dynamic, elastic, and thermodynamic properties of Be Se were investigated with first principles calculations. The phase transition pressure from the zinc blende（B3） to the nickel arsenide（B8） structure of Be Se was determined. The elastic stability analysis suggests that the B3 structure Be Se is mechanically stable in the applied pressure range of 0-50 GPa. Our lattice dynamic calculations show that the B3 structure is lattice dynamically stable under high pressure. Within the quasiharmonic approximation, the thermodynamic properties including the constant volume heat capacity and constant pressure heat capacity are predicted.展开更多
Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6,1.2,and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation p...Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6,1.2,and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer.It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data.The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K,i.e.,the D^u relation,D=C_(0)+λu(u<10 km/s,λ=1.32)in a low pressure region,is approximately parallel with the fitted D^u(λ=1.36)of liquid helium from the experimental data of Nellis et al.Our calculations show that the Hugoniot parameterλis independent of the initial densityρ_(0).The D^u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates to about 18000 K and the ionization degree of the shocked gas helium reaches 10^(-3).展开更多
基金Funded by the National Natural Science Foundation of China(Nos.11447176 and 11447152)the The National Scholastic Athletics Foundation(No.U1230201)the Doctor Foundation of Southwest University of Science and Technology(Nos.13zx7137 and 14zx7167)
文摘The lattice dynamic, elastic, and thermodynamic properties of Be Se were investigated with first principles calculations. The phase transition pressure from the zinc blende（B3） to the nickel arsenide（B8） structure of Be Se was determined. The elastic stability analysis suggests that the B3 structure Be Se is mechanically stable in the applied pressure range of 0-50 GPa. Our lattice dynamic calculations show that the B3 structure is lattice dynamically stable under high pressure. Within the quasiharmonic approximation, the thermodynamic properties including the constant volume heat capacity and constant pressure heat capacity are predicted.
文摘Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6,1.2,and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer.It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data.The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K,i.e.,the D^u relation,D=C_(0)+λu(u<10 km/s,λ=1.32)in a low pressure region,is approximately parallel with the fitted D^u(λ=1.36)of liquid helium from the experimental data of Nellis et al.Our calculations show that the Hugoniot parameterλis independent of the initial densityρ_(0).The D^u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates to about 18000 K and the ionization degree of the shocked gas helium reaches 10^(-3).
