Electronic structure of platinum at ultrahigh pressure

Abstract

Platinum is studied, theoretically, under very high compression. The calculated equation of state is found to agree well with the recent experimental data. At V/V₀ = 0.4, where V₀ is the experimental equilibrium volume, we find a transition from the face centered cubic structure (fcc), found at ambient pressure, to the body centered cubic structure (bcc). The calculated transition pressure is 26 Mbar. The stabilization of the bcc structure is explained by the eigen value sum.     

Laserlike vibrational instability in rectifying molecular conductors

We study the damping of molecular vibrations due to electron-hole pair excitations in donor-acceptor (D-A) type molecular rectifiers. At finite voltage additional nonequilibrium electron-hole pair excitations involving both electrodes become possible, and contribute to the stimulated emission and absorption of phonons. We point out a generic mechanism for D-A molecules, where the stimulated emission can dominate beyond a certain voltage due to the inverted position of the D and A quantum resonances. This leads to current-driven amplification (negative damping) of the phonons similar to laser action. We investigate the effect in realistic molecular rectifier structures using first-principles calculations.     

Mass measurements of neutron-deficient nuclides close to A = 80 with a Penning trap

The masses of ^{80, 81, 82, 83}Y, ^{83, 84, 85, 86, 88}Zr and ^{85, 86, 87, 88}Nb have been measured with a typical precision of 7keV by using the Penning trap setup at IGISOL. The mass of ⁸⁴Zr has been measured for the first time. These precise mass measurements have improved S_p and Q_EC values for astrophysically important nuclides.