Within a movable and orientable rigid rotor model, four interaction potentials of solid deuterium (hydrogen) system from combinations of two isotropic and two anistropic parts are tested by the path integral Monte Carlo method in a constant-pressure ensemble. With the best one of the potentials, the equation of state of deuterium is quantitatively in agreement with the experimental data. For understanding the quantum nature of the solid, the energies of the system at different temperatures are also calculated, the results show strong zero-point motions exist in the solid. As would be expected, the quantum corrections to both the rotational and the translational kinetic energies decrease with increasing temperature, and increase with pressure. © by Allerton Press, Inc.

Cui Tian;Zou Guang-Tian;Whaley K. B.

Chinese Physics Letters

1998

The Raman scattering in Zn 0.74Cd 0.26Se/ZnSe superlattices under hydrostatic pressures up to 4.53 GPa at room temperature has been studied. The pressure-dependences of the ZnSe-like LO-phonon (LO b,) and the Zn 0.74Gd 0.26Se-like LO-phonon (LO w) have been obtained. At 2.7 GPa, the pressure-coefficients of both LO b and LO W phonon energies increase abruptly. The 2LO w-phonon resonance has been observed at 1.82 GPa with 488.0nm excitation for the Zn 0.75Cd 0.25Se/ZnSe superlattices. © by Allerton Press, Inc.

Chi Yuan-Bin;Wang Li-Zhong;Li Yan-Mei;Zou Guang-Tian;Li Wen-Sen;Fan Xi-Wu;Yang Bao-Jun

Chinese Physics Letters

1998

Structure phase transitions of Ba1-xBi2+xTixNb2-xO9 have been observed in the Raman spectra. For the case with x = 0.0, the end member BaBi2Nb2O9 displays a clearly distinct Raman spectrum with respect to the cases with x ≠ 0. Later they have similar Raman spectra as that of other layered ferroelectrics. Therefore, it is proposed that a ferroelectric-nonferroelectric phase transition takes place for the case of BaBi2Nb2O9. A preliminary assignment of the vibration modes is given.

Han J.;Zou G.;Zhao Y.

Solid State Communications

1999

Nanosized chromium disilicide (CrSi 2 ) powder was prepared by the arc plasma method and a subsequent purification process. The as-prepared CrSi 2 powder was characterized by X-ray powder diffraction and transmission electron microscopy. The crystal structure of the powder was also confirmed with infrared spectroscopy. The thermal stability of powders were investigated from room temperature to 1000 °C in air and in a helium atmosphere, indicating that even in the nanosize region this disilicide powder was stable up to 720 °C in air. Analysis of its photovoltage spectra shows that there exist two direct interband transitions in nanosized CrSi 2 grains at 0.782 and 1.148 eV, respectively.

Lu Jinshan;Yang Haibin;Liu Bingbing;Han Jie;Zou Guangtian

Materials Chemistry and Physics

1999

The behaviors of ferroelectric KNbO3 under pressure were studied by in situ dielectric constant measurements in a cubic anvil press up to 11 GPa at low temperatures and by x-ray diffraction in a diamond anvil cell using synchrotron radiation and an imaging plate up to 65 GPa at room temperature. Based on the dielectrical changes, it is suggested that the pressure-induced transitions from the ferroelectric orthorhombic phase to the ferroelectric tetragonal occurs at 8.5 GPa, which in turn, transforms to the paraelectric cubic phase at 11 GPa. All three phases are stable at ambient pressur at room temperature. A new structural transition was found at around 40 GPa. The high pressure phase appears to adopt the GdFeO3-type structure (space group: Pnma), which is one of the distorted perovskite structures. The sequence of phase transition in KNbO3 is therefore such that orthorhombic → tetragonal → cubic → orthorhombic (GdFeO3-type) with increasing pressure at room temperature.

Kobayashi Y.;Endo S.;Ashida T.;Deguchi K.;Ming L. C.;Kikegawa T.;Zou G.

Journal of the Korean Physical Society

1999

Semiconducting chromium disilicide (CrSi 2 ) nanocrystals were prepared by the arc plasma method, and characterized by X-ray diffraction and transmission electron microscopy. The pressure-reduced semiconductor-metal transition in CrSi 2 nanocrystals was investigated in a diamond anvil cell by electrical resistance measurements at high pressure. The pressure dependence of resistance at room temperature in the pressure range of 0-10 GPa revealed an exponential decrease up to 3.2 GPa, indicating a linear closing of the energy gap, followed by an almost pressure-independent metallic regime. This phase transition is discussed in terms of previous band structure calculations.

Cui Qiliang;Yang Haibin;Liu Bingbing;Zou Guangtian;Lu Jinshan

Materials Letters

1999

Ta/anodized Ta2 O5/Al is used as metal-insulator-metal (MIM) element, in experiments. The current -voltage (I-V) characteristic of the MIM element depends on the chamber pressure in heat-treating anodixed Ta2 O5 film. Good nonlinear I-V characteristic has been obtained in the pressure range from 10^-2 to 10^-4 Torr. Meanwhile, the conductivity coefficient α of the Poole-Frenkel (PF) equation which describes the I-V characteristic can be regulated by about two orders of magnitude in this pressure range, while the non-linearity coefficient β of the PF equation is not affected by the chamber pressure. * Supported by the National Natural Science Foundation of China under Grant Nos, C9576012 and 59631060.

Liu Hong-Wu;Gao Chun-Xiao;Hui Wang;Cui Qi-Liang;Zou Guang-Tian;Huang Xi-Min

Chinese Physics Letters

1999

The E-BN film named after the method by which it is obtained (E=Explosion). During the BN film deposition, a model of phase transition from E-BN to c-BN was suggested and then the c-BN nucleation during the deposition can be explained by this model. The film has very good adhesion due to the phase transition.

Zhu Pinwen;Zhao Yongnian;Zou Guangtian;He Zhi

Gaoya Wuli Xuebao Chinese Journal of High Pressure Physics

2000

The in situ behavior of distorted perovskite La0.5-xBixCa0.5MnO3 (x=0.1, 0.15, 0.2) under high pressure has been studied by energy-dispersive X-ray diffraction in a diamond anvil cell. An abnormal change of the 202-040 d-spacing ascribed to the disappearance of the distortion mode Q2 in the MnO6 octahedra is observed at 1.2, 1.4, and 1.6 GPa, respectively, and it results in a reduction of the Jahn-Teller distortion commonly existing in the manganites. Effect of the unique 6s² long-pair character of the Bi³⁺ ion on the pressure dependence of the lattice distortion is discussed. © 2001 Academic Press.

Wang X.;Pan Y. W.;Cui Q. L.;Zhang J.;Gao W.;Zou G. T.

Journal of Solid State Chemistry

2001

Nanoparticles of γ-Fe 2O 3 with a mean particle size of 9 nm (an average nanograin size of 4 nm) have been prepared by an electrical explosion method through one-step. The particles were nearly equiaxed. The particle size distribution fits with log-normal distribution law as identified by SAXS. The coercivity and the saturation magnetization of the sample were determined to be as about 30% of those of the bulk materials by VSM. A possible mechanism for the formation of the γ-Fe 2O 3 was proposed. © 2001 Elsevier Science Ltd.

Wang Qun;Shi Jianlin;Yang Haibin;Zou Guangtian

Materials Research Bulletin

2001