Studies on CsBr with Synchrotron Radiation Under Ultrahigh Pressure up to 115GPa

In situ high pressure energy dispersive x-ray diffraction experiments have been carried out on CsBr by using diamond anvil cell device with synchrotron radiation source.The maximum pressure is 115 GPa.The structure of CsBr is changed from simple cubic phase to tetragonal phase at pressure about 53 GPa,marked by the splitting of its strongest diffraction line(110).At pressure above 98GPa,the color change of CsBr from transparent to red-brown was observed.No pressure-induced transition from insulator to metal is found at higher pressure up to 115GPa.

Pressure Induced Phase Transition in TiB

In situ high pressure x-ray diffraction and electrical resistance experiments on TiB have been carried out by using a diamond anvil cell device. The results revealed that the sample undergoes a first-order phase transition at pressures of 3.5-5.0 Gpa and 4.0-5.5 Gpa for the x-ray diffraction and electrical resistance experiments, respectively. The parameters of the state equation are calculated before and after the phase transition and compared with the values calculated by Mohn et al. [J. Phys. C: Solid State Phys. 21(1988)2829] using the augmented spherical wave method.

X-Ray Diffraction Study of Carbon Nanotubes Under High Pressure

The structure and physical properties of carbon nanotubes have been investigated by using in situ high pressure energy dispersive x-ray diffraction with synchrotron radiation at pressures up to 50.7 GPa.At atmospheric pressure,the structure of carbon nanotubes is similar to the hexagonal close-packed lattice of graphite with the interplanar spacing of the diffraction line(002)d002=0.3404 nm and that of the line(100)d100=0.2116 nm.According to the high pressure x-ray diffraction results,the diffraction line(002)is broadened and weakened above 8 GPa,and carbon nanotubes become partly amorphous.When the pressures of 10 and 20 GPa are decreased down to zero,the diffraction line(002)is partly recovered.While at the maximum pressure of 50.7 GPa,they entirely become amorphous and this amorphous transition is irreversible.We used the equation of state of Birch-Murnaghan to fit the P-V data of carbon nanotubes and obtained the bulk modulus K0=54.3±3.2 GPa(at K'0=4.0).

Optical Absorption and X-Ray Diffraction Studies of Sulfur Under High Pressure

In situ high pressure optical absorption measurements of sulfur have been carried out by using DAC device with a TASCO V-550 UV-VIS spectrophotometer at pressures up to 41.6 GPa.The curves of absorption edge vs pressure were obtained,in which there are two turning points at about 5 and 12 GPa,corresponding to two changes of colour in the optical observation:one is from yellow to red and the other from red to black at 5-6.5 and 10-12 GPa,respectively.The absorption edge reaches above 800 nm when the pressure is increased to 23 GPa.The structure and phase transitions have also been investigated by using in situ high pressure energy-dispersive x-ray diffraction with synchrotron radiation at pressures up to 33.7 GPa.No structure phase transition occurs at 5-6 GPa,but there is a new high-pressure phase,caused probably by the reorieutation or ordering of Sq.

Raman Study of Nitrogen at High Pressure

Raman spectra of the nitrogen loaded in a diamond anvil cell with the compressed gas have been investigated at the pressure up to 40GPa.Pressure was measured in terms of the ruby fluorescence.The curve of frequency vs pressure was obtained by micro-Raman spectrometer.According to the experimental results,the frequency of two stretching mode peaks increases steadily from 2340 and 2347cm^(-1) at 5.2 GPa to 2396 and 2434 cm^(-1) at 40 GPa,respectively.The interval between two peaks also increases gradually with pressure increasing.A new peak(2402cm^(-1))of the stretching mode was observed near 40 GPa,which may be associated with the distortion of the Pm3n structure or the formation of low-symmetry structure.

High Pressure Raman Study of Phase Transitions on Solid Benzene Using Raman Notch Filter Set

A high-throughput Haman notch filter set has been manufactured and used to collect the Raman scattering signals of pressure-hiduced phase transitions of solid benzene in a diamond anvil cell up to 15 GPa at room temperature.The changes in the profiles as well as the frequencies of Raman scattering spectra are observed and enable us to determine the phase transition.

Pressure-Induced Amorphous Transition of Li_(2)Ge_(7)O_(15) Crystal

Pressure-induced amorphous transition of Li_(2)Ge_(7)O_(15)(LGO)crystal has been investigated by using in situ high pressure energy dispersive x-ray diffraction with synchrotron radiation at the pressure up to 21.6 GPa.Diamond anvils were used to generate high pressure.Pressure was measured in terms of the diffraction of Pt as an internal pressure standard.The crystal structure of LGO is an orthorhombic lattice at atmospheric pressure.According to the high pressure x-ray diffraction results,new diffraction lines begin to appear and LGO undergoes an intermediate phase transition at the pressure of 12.9 GPa.But,the diffraction lines disappear wholly and LGO becomes an amorphous phase at the pressure of above 14.8 GPa.This amorphous transition is irreversible.