Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userVan der Waals effects on grazing incidence fast atom diffraction for H/LiF(001)
57
0
0.0
(
0
)
Added by
Maria Silvia Gravielle
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We theoretically address grazing incidence fast atom diffraction (GIFAD) for H atoms impinging on a LiF(001) surface. Our model combines a description of the H-LiF(001) interaction obtained from Density Functional Theory calculations with a semi-quantum treatment of the dynamics. We analyze simulated diffraction patterns in terms of the incidence channel, the impact energy associated with the motion normal to the surface, and the relevance of Van der Waals (VdW) interactions. We then contrast our simulations with experimental patterns for different incidence conditions. Our most important finding is that, for normal energies lower than 0.5 eV and incidence along the <100> channel, the inclusion of Van der Waals interactions in our potential energy surface yields a greatly improved accord between simulations and experiments. This agreement strongly suggests a non-negligible role of Van der Waals interactions in H/LiF(001) GIFAD in the low-to-intermediate normal energy regime.
rate research
Read More
Diffraction patterns produced by grazing scattering of fast atoms from insulator surfaces are used to examine the atom-surface interaction. The method is applied to He atoms colliding with a LiF(001) surface along axial crystallographic channels. The projectile-surface potential is obtained from an accurate DFT calculation, which includes polarization and surface relaxation. For the description of the collision process we employ the surface eikonal approximation, which takes into account quantum interference between different projectile paths. The dependence of projectile spectra on the parallel and perpendicular incident energies is experimentally and theoretically analyzed, determining the range of applicability of the proposed model.
Single crystalline samples of the van der Waals antiferromagnet CrPS4 were studied by measurements of specific heat and comprehensive anisotropic temperature- and magnetic field-dependent magnetization. In addition, measurements of the heat capacity and magnetization were performed under pressures of up to ~21 kbar and ~14 kbar respectively. At ambient pressure, two magnetic transitions are observed, second order from a paramagnetic to an antiferromagnetic state at TN ~ 37 K, and a first-order spin reorientation transition at T* ~ 34 K. Anisotropic H - T phase diagrams were constructed using the M(T,H) data. As pressure is increased, TN is weakly suppressed with dTN/dP ~ -0.1 K/kbar. T*, on the other hand, is suppressed quite rapidly, with dT*/dP ~ -2 K/kbar, extrapolating to a possible quantum phase transition at Pc ~ 15 kbar.
We report structural, physical properties and electronic structure of van der Waals (vdW) crystal VI3. Detailed analysis reveals that VI3 exhibits a structural transition from monoclinic C2/m to rhombohedral R-3 at Ts ~ 79 K, similar to CrX3 (X = Cl, Br, I). Below Ts, a long-range ferromagnetic (FM) transition emerges at Tc ~ 50 K. The local moment of V in VI3 is close to the high-spin state V3+ ion (S = 1). Theoretical calculation suggests that VI3 may be a Mott insulator with the band gap of about 0.84 eV. In addition, VI3 has a relative small interlayer binding energy and can be exfoliated easily down to few layers experimentally. Therefore, VI3 is a candidate of two-dimensional FM semiconductor. It also provides a novel platform to explore 2D magnetism and vdW heterostructures in S = 1 system.
The exfoliation of two naturally occurring van der Waals minerals, graphite and molybdenite, arouse an unprecedented level of interest by the scientific community and shaped a whole new field of research: 2D materials research. Several years later, the family of van der Waals materials that can be exfoliated to isolate 2D materials keeps growing, but most of them are synthetic. Interestingly, in nature plenty of naturally occurring van der Waals minerals can be found with a wide range of chemical compositions and crystal structures whose properties are mostly unexplored so far. This Perspective aims to provide an overview of different families of van der Waals minerals to stimulate their exploration in the 2D limit.
Molecular-scale manipulation of electronic/ionic charge accumulation in materials is a preeminent challenge, particularly in electrochemical energy storage. Layered van der Waals (vdW) crystals exemplify a diverse family of materials that permit ions to reversibly associate with a host atomic lattice by intercalation into interlamellar gaps. Motivated principally by the search for high-capacity battery anodes, ion intercalation in composite materials is a subject of intense study. Yet the precise role and ability of heterolayers to modify intercalation reactions remains elusive. Previous studies of vdW hybrids represented ensemble measurements at macroscopic films/powders, which do not permit the isolation and investigation of the chemistry at individual 2-dimensional (2D) interfaces. Here, we demonstrate the intercalation of lithium at the level of individual atomic interfaces of dissimilar vdW layers. Electrochemical devices based on vdW heterostructures comprised of deterministically stacked hexagonal boron nitride, graphene (G) and molybdenum dichalcogenide (MoX2; X = S, Se) layers are fabricated, enabling the direct resolution of intermediate stages in the intercalation of discrete heterointerfaces and the extent of charge transfer to individual layers. Operando magnetoresistance and optical spectroscopy coupled with low-temperature quantum magneto-oscillation measurements show that the creation of intimate vdW heterointerfaces between G and MoX2 engenders over 10-fold accumulation of charge in MoX2 compared to MoX2/MoX2 homointerfaces, while enforcing a more negative intercalation potential than that of bulk MoX2 by at least 0.5 V. Beyond energy storage, our new combined experimental and computational methodology to manipulate and characterize the electrochemical behavior of layered systems opens up new pathways to control the charge density in 2D (opto)electronic devices.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
