ترغب بنشر مسار تعليمي؟ اضغط هنا

The influence of Pauli blocking effects on the properties of dense hydrogen

64   0   0.0 ( 0 )
 نشر من قبل David Blaschke
 تاريخ النشر 2008
  مجال البحث فيزياء
والبحث باللغة English
 تأليف W. Ebeling




اسأل ChatGPT حول البحث

We investigate the effects of Pauli blocking on the properties of hydrogen at high pressures, where recent experiments have shown a transition from insulating behavior to metal-like conductivity. Since the Pauli principle prevents multiple occupation of electron states (Pauli blocking), atomic states disintegrate subsequently at high densities (Mott effect). We calculate the energy shifts due to Pauli blocking and discuss the Mott effect solving an effective Schroedinger equation for strongly correlated systems. The ionization equilibrium is treated on the basis of a chemical approach. Results for the ionization equilibrium and the pressure in the region 4.000 K < T < 20.000 K are presented. We show that the transition to a highly conducting state is softer than found in earlier work. A first order phase transition is observed at T < 6.450 K, but a diffuse transition appears still up to 20.000 K.

قيم البحث

اقرأ أيضاً

We investigate the effects of Pauli blocking on thermalization process of relativistic plasma by solving relativistic Uehling-Uhlenbeck equations with QED collision integral for all binary and triple processes. With this purpose we consider nonequili brium initial state of plasma to be strongly degenerate. We found that when electron-positron annihilation is active, initial plasma degeneracy is quickly destroyed. As a result in a wide range of final temperatures ranging from nonrelativistic to mildly relativistic $0.1 m_e c^2 leq k_B Tleq 10 m_e c^2$ thermalization is not affected by Pauli blocking. Conversely, when electron-positron annihilation process is inactive, thermalization process in such degenerate plasma is strongly affected by Pauli blocking. This is possible either in a nonrelativistic plasma, with equilibrium temperature $k_B Tleq 0.3 m_e c^2$, or in photon-electron plasma. In these cases all reaction rates are strongly suppressed by Pauli blocking and thermalization does not occur until electrons can populate energy states above the Fermi energy. Soon after this happens thermalization proceeds suddenly in an avalanche-like process.
We study the thermophysical properties of warm dense hydrogen using quantum molecular dynamics simulations. New results are presented for the pair distribution functions, the equation of state, the Hugoniot curve, and the reflectivity. We compare wit h available experimental data and predictions of the chemical picture. Especially, we discuss the nonmetal-to-metal transition which occurs at about 40 GPa in the dense fluid.
Spontaneous decay of an excited atomic state is a fundamental process that originates from the interaction between matter and vacuum modes of the electromagnetic field. The rate of decay can thus be engineered by modifying the density of final states of the joint atom-photon system. Imposing suitable boundary conditions on the electromagnetic field has been shown to alter the density of vacuum modes near the atomic transition, resulting in modified atomic decay rates. Here we report the first experimental demonstration of suppression of atomic radiative decay by reducing the density of available energy-momentum modes of the atomic motion when it is embedded inside a Fermi sea.
Pauli blocking is carefully investigated for the processes of $NN rightarrow N Delta$ and $Delta rightarrow N pi$ in heavy-ion collisions, aiming at a more precise prediction of the $pi^-/ pi^+$ ratio which is an important observable to constrain the high-density symmetry energy. We use the AMD+JAM approach, which combines the antisymmetrized molecular dynamics for the time evolution of nucleons and the JAM model to treat processes for $Delta$ resonances and pions. As is known in general transport-code simulations, it is difficult to treat Pauli blocking very precisely due to unphysical fluctuations and additional smearing of the phase-space distribution function, when Pauli blocking is treated in the standard method of JAM. We propose an improved method in AMD+JAM to use the Wigner function precisely calculated in AMD as the blocking probability. Different Pauli blocking methods are compared in heavy-ion collisions of neutron-rich nuclei, ${}^{132}mathrm{Sn}+{}^{124}mathrm{Sn}$, at 270 MeV/nucleon. With the more accurate method, we find that Pauli blocking is stronger, in particular for the neutron in the final state in $NN rightarrow N Delta$ and $ Delta to Npi$, compared to the case with a proton in the final state. Consequently, the $pi^-/pi^+$ ratio becomes higher when the Pauli blocking is improved, the effect of which is found to be comparable to the sensitivity to the high-density symmetry energy.
The ability of atomic hydrogen to chemisorb on graphene makes the latter a promising material for hydrogen storage. Based on scanning tunneling microscopy techniques, we report on site-selective adsorption of atomic hydrogen on convexly curved region s of monolayer graphene grown on SiC(0001). This system exhibits an intrinsic curvature owing to the interaction with the substrate. We show that at low coverage hydrogen is found on convex areas of the graphene lattice. No hydrogen is detected on concave regions. These findings are in agreement with theoretical models which suggest that both binding energy and adsorption barrier can be tuned by controlling the local curvature of the graphene lattice. This curvature-dependence combined with the known graphene flexibility may be exploited for storage and controlled release of hydrogen at room temperature making it a valuable candidate for the implementation of hydrogen-storage devices.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا