A.W. Webb

Bio: A.W. Webb is an academic researcher from United States Naval Research Laboratory. The author has contributed to research in topics: Magnetic susceptibility & Band gap. The author has an hindex of 3, co-authored 3 publications receiving 77 citations.

Monolayer behaviour in bulk ReS2 due to electronic and vibrational decoupling

Abstract: Monolayers of transition metal dichalcogenides have emerged as interesting two-dimensional materials. Here, the authors show that in a new member of this family of compounds, rhenium disulphide, the layers in the bulk are vibrationally and electronically decoupled, so that they behave almost as monolayers.

High-pressure polymorphism of the copper(I) halides: A neutron-diffraction study to ∼10 GPa

Abstract: The structural changes within the copper(I) halides induced by hydrostatic pressure have been investigated using the powder neutron-diffraction technique. The expected transition from the ambient zinc-blende structure with tetrahedral coordination to the octahedrally coordinated rocksalt structure is observed in both CuCl and CuBr. No rocksalt phase is observed in CuI, presumably due to the limited maximum pressure of our apparatus (\ensuremath{\sim}10 GPa). The lower symmetry phases which occur as intermediate structures between the zinc-blende and rocksalt phases have been studied in detail. CuCl and CuI undergo abrupt transitions whilst CuBr has three sluggish transitions, involving extensive coexistence of neighboring phases. There is one intermediate phase in CuCl (CuCl-IV), two in CuBr (CuBr-IV and CuBr-V) and at least two in CuI (CuI-IV and CuI-V). Three different structure types have been identified, in space groups Pa3\ifmmode\bar\else\textasciimacron\fi{} (CuCl-IV and CuBr-V), P4/nmm (CuBr-IV and CuI-V) and R3\ifmmode\bar\else\textasciimacron\fi{}m (CuI-IV). The intermediate structures all retain the tetrahedral cation coordination of the ${\mathrm{Cu}}^{+}$, though the environment is rather more distorted in CuCl and CuBr than in CuI. The evolution of the structures of these I-VII compounds is very different from that observed in the more covalent II-VI and III-V systems.

Building two-dimensional materials one row at a time: Avoiding the nucleation barrier.

Abstract: Assembly of two-dimensional (2D) molecular arrays on surfaces produces a wide range of architectural motifs exhibiting unique properties, but little attention has been given to the mechanism by which they nucleate. Using peptides selected for their binding affinity to molybdenum disulfide, we investigated nucleation of 2D arrays by molecularly resolved in situ atomic force microscopy and compared our results to molecular dynamics simulations. The arrays assembled one row at a time, and the nuclei were ordered from the earliest stages and formed without a free energy barrier or a critical size. The results verify long-standing but unproven predictions of classical nucleation theory in one dimension while revealing key interactions underlying 2D assembly.