High-Pressure Research On Cycloalkanes

High-pressure physics is a subject that research material under high-pressure conditions in the state, the status changes and physical nature. Is a new branch of physics which based on the development of material science, astronomy and geophysics. Pressure, temperature and chemical composition are the three basic parameters of material existence. The pressure as an independent in the temperature and chemical composition of the third physics parameters can be very effective in the internal atomic spacing material changes, in the electronic track adjacent overlap, increase further material change in the crystal structure, and electronic structure of atoms (molecules) the interaction between high pressure , so that they will reach equilibrium under high pressure, form a new phase. The new phase is different from the structure of atmospheric material, they emergence of some new physical and chemical properties.High-pressured research may discover the new phenomenon which material under atmospheric pressures cannot display; discover the new rules; the new performance; even discovers the new material; provided new way to study the material's nature under the atmospheric pressure and explanation atmospheric pressure phenomenon.In recent years the organic molecule crystal material has been widespread concern, its latent value has gradually being recognized. We use the diamond anvil cell (DAC) equipment, high-pressure synchrotron radiation facility, in situ high-pressure Raman spectroscopy device to research the simple system of small organic molecules - Cycloalkanes in cyclopentane, cyclohexane, cycloheptane, cyclooctane. To further study the organic molecular material provides the basic high pressure empirical datum.(1)High-pressure in situ synchrotron radiation diffraction and high-pressure in situ Raman spectra are used in the system cycloalkanes cyclopentane, cyclohexane, cycloheptane and cyclooctane to carry out the system's structure and the lattice vibration under high pressure. These two way can be complementary to prove to be from a different side to deepen Cycloalkanes under high pressure, structure and the nature.(2)High-pressure in situ Raman spectra study of cyclopentane have been carried out using diamond anvil cell at room temperature. The pressure is up to 42.5GPa. With the increase of pressure, the cyclopentane taken place the liquid-solid phase transition at 1.78GPa. At 2.78 GPa, 9.7 GPa, 11.2 GPa and 17.1 GPa the Raman spectra have a significant change. Cyclopentane the vibration mode is very sensitive to pressure, the breathe vibration is particularly sensitive. The high pressure in situ synchrotron radiation research of cyclopentane found that between 3.33 and 7.50 GPa it may be inclined to monoclinic structure, at 7.50 GPa there may be a phase trasition, the new phase of high pressure may be triclinic structure. Give lattice parameters of two-phase.(3) High pressure in situ synchrotron radiation research of cyclohexane has been carried out using diamond anvil cell at room temperature. Between 4.74 and 9.19 GPa, cyclohexane may be inclined to monoclinic structure. At 9.19 GPa, there is a phase change. As the number of new phase'speak is less, it is impossible to infer the structure.(4) High-pressure in situ Raman spectra study of cycloheptane have been carried out using diamond anvil cell at room temperature. With the increase of pressure, the cycloheptane taken place the liquid-solid phase transition at 0.53GPa. During 3.45-5.58GPa, both the curve of Raman Frequence- Pressure and FWHM-Pressure are have inflexions, cycloheptane may have a solid-solid phase transition at this section. The high pressure in situ synchrotron radiation research of cycloheptane found that between 1.68 and 5.93 GPa it may be inclined to monoclinic structure, at 5.93 GPa there may be a phase trasition, the new phase of high pressure may be triclinic structure.(5) High-pressure in situ Raman spectra study of cyclooctane have been carried out using diamond anvil cell at room temperature. With the increase of pressure, the cyclooctane taken place the liquid-solid phase transition at 0.87 GPa. From the figure of Pressure-Raman frequency, we can clear find the cure of P-νhave inflexion at about 4.92 GPa. Before and after 4.92 GPa, clear find the ring"breath"vibration connect with C-H scissors vibration, is the most sensitive Raman vibration mode to pressure;the ring"breath"vibration & retortion angle & C-H rock vibration don't sensitive to pressure. the structural behaviors of cyclooctane under high pressure have been studied in-situ by the synchrotron X-ray source in DAC up to 40.2GPa at room temperature. When the pressure increases, the phase transitions along triclinic phase to tetragonal phase till to the amorphous phase occur in turn at about 6.0GPa and above 18.2GPa. The amorphous phase is kept till to 40.2GPa. After decompressing pressure, the phase transitions of cyclooctane occurred with the pressure increasing are irreversible.