Showing papers by "J. Mayers published in 2008"
TL;DR: Measurements of the proton momentum distribution n(p) in water from ambient conditions to above the supercritical point are compared with theoretical calculations based on a recently developed polarizable water model, which accurately predicts the n( p) for the dilute phases.
Abstract: Measurements of the proton momentum distribution n(p) in water from ambient conditions to above the supercritical point are compared with theoretical calculations based on a recently developed polarizable water model. The n(p) along the H-bond direction is narrower in the dense phases, and approaches that of the isolated molecule in the more dilute phases. The theoretical model, which includes only electrostatic interactions, is unable to explain the softening of the local potential experienced by the proton in the dense phases, but it accurately predicts the n(p) for the dilute phases.
75 citations
TL;DR: In this article, the momentum distribution in KD2PO4 (DKDP) was measured using neutron Compton scattering above and below the weakly first-order paraelectric-ferroelectric phase transition (T=229 K).
Abstract: The momentum distribution in KD2PO4 (DKDP) has been measured using neutron Compton scattering above and below the weakly first-order paraelectric–ferroelectric phase transition (T=229 K). There is very little difference between the two distributions, and no sign of the coherence over two locations for the proton observed in the paraelectric phase, as in KH2PO4 (KDP). We conclude that the tunnel splitting must be much less than 20 meV. The width of the distribution indicates that the effective potential for DKDP is significantly softer than that for KDP. As electronic structure calculations indicate that the stiffness of the potential increases with the size of the coherent region locally undergoing soft mode fluctuations, we conclude that there is a mass-dependent quantum coherence length in both systems.
19 citations
TL;DR: In this paper, the same theory was used to describe the results of all three experiments in a quantitative way and it was shown that this theory can describe the result of all the three experiments, in all cases highly oriented pyrolytic graphite was used as a testing material.
Abstract: Received 21 April 2008; revised manuscript received 25 May 2008; published 2 July 2008Recoil effects have been observed for neutron and electron scatterings, and in photoemission. In all caseshighly oriented pyrolytic graphite was used as a testing material and dependencies of recoil effects on thecrystal orientation were found but these results have, so far, not been compared. We show that the same theorycan describe the results of all three experiments in a quantitative way.DOI: 10.1103/PhysRevB.78.024301 PACS number s : 79.60. i, 78.70.Nx, 79.20.Kz
10 citations