Analysis of K-prime equations of state

In the present communication, we introduce a new K-prime equation of state (EoS), which can be used to understand the interior of the Earth. The newly developed EoS is found to yield similar results as given by Stacey K-prime EoS and Keane EoS, in reference to the seismological data. However, the zero pressure and infinite pressure extrapolation of higher pressure derivatives of bulk modulus are found different for different K-prime EoS.     

Investigation of structural and electronic properties of β- HgS: Molecular dynamics simulations

The pressure induced phase transition of β-HgS is studied using an ab initio molecular dynamics simulation. The structural phase transformation from the zinc-blende structure to the NaCl-type structure (space group $Fm\overline{3}m$) and from this structure to CsCl-type structure ($Pm\overline{3}m$) with the application of hydrostatic pressure is predicted. Additionally, the electronic properties of HgS and various physical properties such as the lattice constants, the bulk modulus and the pressure derivative of the bulk modulus are revealed. Furthermore, these phase transitions are obtained using the total energy and enthalpy calculations. According to these calculations these transformations are occurring at about 20?GPa and 28?GPa for $F\overline{4}3m$ →$Fm\overline{3}m$ and $Fm\overline{3}m$ →$Pm\overline{3}m$, respectively.     

Applicability of equation of state in extreme compression region and study of diatomic solids under pressure

In the present study, the expression of first pressure derivative of bulk modulus B′?earlier derived by Goyal and Gupta EoS [7] is corrected and the validity of the EoS is then verified in extreme compression region. The expressions of second and third order pressure derivative $(B^{{}^{″}},B^{″\prime })$of bulk modulus are obtained. The values of B′, B²B? to BB″,?Grunesien parameters?λ_∞,?γ_∞,?q_∞ at infinite pressure (P?→?∞)?are calculated using the identities [11–13] to check the validity of the equation in extreme compression region. The Goyal and Gupta EoS is then used to study the volume compression in diatomic solids, LiH and MgO. The values of pressure, bulk modulus and its first order pressure derivative at different compressions are calculated and compared with the results obtained from Hama–Suito EoS. The results justify the validity of the present EoS in high pressure region and the results for diatomic solids are also found in good consistency with the compared results.     

Temperature-dependent cross sections for meson–meson nonresonant reactions in hadronic matter

We present a potential of which the short-distance part is given by one gluon exchange plus perturbative one- and two-loop corrections and of which the large-distance part exhibits a temperature-dependent constant value. The Schrödinger equation with this temperature-dependent potential yields a temperature dependence of the mesonic quark–antiquark relative-motion wave function and of meson masses. The temperature dependence of the potential, the wave function and the meson masses brings about temperature dependence of cross sections for the nonresonant reactions $\pi \pi \to \rho \rho$ for $I=2$, $KK\to K^{*}{K}^{*}$ for $I=1$, $K{K}^{*}\to K^{*}{K}^{*}$ for $I=1$, $\pi K\to \rho K^{*}$ for $I=3/2$, $\pi K^{*}\to \rho K^{*}$ for $I=3/2$, $\rho K\to \rho K^{*}$ for $I=3/2$ and $\pi K^{*}\to \rho K$ for $I=3/2$. As the temperature increases, the rise or fall of peak cross sections is determined by the increased radii of initial mesons, the loosened bound states of final mesons, and the total-mass difference of the initial and final mesons. The temperature-dependent cross sections and meson masses are parametrized.     

Debye temperature of gold under high pressure determined by X-ray powder diffraction method

In order to verify pressure scales of gold, the atomic-volume dependence of Debye temperature under high pressure up to 14 GPa was measured based on Debye–Waller factor by an X-ray diffraction method. High-pressure and high-temperature X-ray powder diffraction patterns were collected by an energy-dispersive method using synchrotron radiation. The X-ray Debye temperature under high pressure was calculated from the integrated intensity ratio between the diffraction patterns collected at two different temperatures. The atomic-volume dependence of the Debye temperature obtained in the present study was consistent with that predicted by a first-principles calculation, in which Debye temperature and Grüneisen parameter of the volume at ambient condition were ${\Theta }_{D0}=180K$ and ${\gamma }_0=3.16$, respectively.     

Magnetic study of low-temperature phase of UCu2Ge2

Magnetization and phase sensitive AC susceptibility was measured for the annealed and as-cast samples of ferromagnetic UCu₂Ge₂, $T_C=107K$. Special attention was paid to the low temperature range, $T<50K$, which is interesting due to the magnetization decrease and frozen AC response. The hysteresis loops showed a remanence of ≈87% and a fast, thermally activated decrease in the coercivity field. Thermoremanent magnetization at 4.3 K decayed with the relaxation time ≈1110³ s. The strong increase of the ${\chi }_{AC}$ with the amplitude of the driving field was observed. All these results point to a very large anisotropy of the compound at the lowest temperatures. Phase transition to the randomly canted ferromagnetic phase at $T\approx 55K$ was detected in the measurement of the third order non-linear susceptibility. It is concluded that the origin of the transition is the strong temperature dependence of magnetic anisotropy.