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In a recent Letter Scanlon and Watson reported their first principles results on hydrogen in Cu2O. Their main conclusions are: (1) an interstitial H in Cu2O prefers to occupy the tetrahedral site, which is coordinated with four Cu cations, in all three charge states (+1, neutral, and -1); (2) H will bind with a Cu vacancy and form an electrically active H-VCu defect complex, which is amphoteric with (+/0) and (0/-)transition levels at Ev + 0.1 and Ev + 1.1 eV, respectively. However, these two conclusions contradict two generally observed behaviors of H in oxides: (i) cationic H usually binds with an O atom, forming a single O-H bond, while the anionic H usually binds with cations with multi-coordination; (ii) H usually passivates cation vacancies in oxides. In this Comment, we explicitly show that with charge state +1, H prefers to bind with a single O anion rather than with four Cu cations and that H-VCu does not induce any defect levels inside the band gap.
A recent paper of Dias and Silvera (DS) reports on production of metallic hydrogen in a diamond anvil cell at 495 GPa at 5.5 and 83 K. The results are implied to have a great impact on energy and rocketry. Here we argue that the presented (very scarc
We comment on a recent paper published by McWilliams et al claiming that high-pressure/high-temperature hydrogen is a semi-conductor or semi-metal, in conflict with all earlier measurements on this system which show that it is metallic. We point out
Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to
Hydrogen is the most abundant element in the universe, and its properties under conditions of high temperature and pressure are crucial to understand the interior of of large gaseous planets and other astrophysical bodies. At ultra high pressures sol
The reported diffusion constants for hydrogen in silicon vary over six orders of magnitude. This spread in measured values is caused by the different concentrations of defects in the silicon that has been studied. Hydrogen diffusion is slowed down as