Free electron gas under high pressure

High-momentum components and temperature dependence of the Compton profile of beryllium

“…Thus, the Compton profile at a high temperature is narrower than at a low temperature. Similar, but more dramatic effects can be introduced by high pressure, as has recently been demonstrated by Hämäläinen et al 10 Second, when the periodic potential of the ion lattice is taken into account, part of the electron momentum density is transferred away from the first Brillouin zone to the socalled high-momentum components. Their origin can be thought of the electron wave functions being Bragg scattered by the potential.…”

“…This is the general trend in all experimental Compton profiles and the reason is believed to lie in the electron-electron correlation effects. 1,5,9,10 The high-momentum components can be seen as two peaks located at the momenta around p z ϭϮ2 a.u. These two distinctive peaks originate from the Gϭ͓110͔ reciprocal lattice vector, although there are also other lowerlying components that are not as prominent as these two.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] The quantity measured in these experiments is the double-differential cross section for photon scattering, which is directly related to the so-called Compton profile J(p z ). The Compton profile, in turn, is related to the momentum density N(p) of the electrons in the system under study by being the integral of N(p) over two dimensions p x and p y .…”

“…Compton scattering is not limited by any of these conditions, and is well suited for temperature-or pressure-dependent studies. 9,10 A finite temperature has several effects on the electron momentum density. First of all, the crystal lattice expansion corresponds to a shrinkage of the reciprocal lattice, which means that the electrons at a finite temperature will be confined to states with a smaller momentum than they are at T ϭ0 K. Second, the vibration of the ions in the crystal around their equilibrium positions effectively smears out the lattice potential.…”

Electronic stucture of methane hydrate studied by Compton scattering

“…During the last decade the Compton scattering technique has been applied to increasingly complex materials, such as quasicrystals, perovskites, and fullerenes. [10][11][12] Also temperature 13,14 and pressure effects 12,15,16 on Compton profiles have been studied. Recently, Itou et al 17 reported on the Compton scattering experiments on covalently bonded polycrystalline Ba 8 Si 46 clathrate, a compound which is isostructural to the hydrates.…”