Search results for "Surfaces"
showing 10 items of 2837 documents
Spin transport across antiferromagnets induced by the spin Seebeck effect
2018
For prospective spintronics devices based on the propagation of pure spin currents, antiferromagnets are an interesting class of materials that potentially entail a number of advantages as compared to ferromagnets. Here, we present a detailed theoretical study of magnonic spin current transport in ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics simulations. The relevant length scales of magnonic spin transport in antiferromagnets are determined. We demonstrate the transfer of angular momentum from a ferromagnet into an antiferromagnet due to the excitation of only one magnon branch in the antiferromagnet. As an experimental system, we ascertain the transport acr…
Phase Stability of Lanthanum Orthovanadate at High Pressure
2016
The journal of physical chemistry / C 120(25), 13749 - 13762(2016). doi:10.1021/acs.jpcc.6b04782
Modelling of phase transitions and reaction at CO adsorption on oxygen precovered Pd(111)
2006
Abstract Using the interaction parameters up to the third neighbors and activated form of O and CO diffusion and their reaction, the model has been proposed for Monte-Carlo simulations describing the catalytic O + CO → CO2 reaction and occurring phase transitions on Pd(1 1 1) surface. Upon adsorption of CO the pre-adsorbed oxygen transforms from p(2 × 2)O phase into 3 × 3 R 30 O ° and 3 × 3 R 30 O ° → p ( 2 × 1 ) O phases in the limit of room and moderate temperatures, respectively. We demonstrate that the kinetic effects determine both the occurrence of the p(2 × 1)O and disappearance of the 3 × 3 R 30 O ° phases at moderate and low temperatures, respectively. Using reaction rate as a fit …
A grand ensemble Monte Carlo study of metal adsorption on a (110) bcc substrate
1992
Abstract The multilayer adsorption of a metal on a (110) bcc substrate has been studied by a grand-canonical Monte Carlo simulation in continuous, three-dimensional space. The obtained values of the critical parameters are compared with the results of a similar 2D Monte Carlo calculation and are interpreted in the spirit of the theory of Asada. A sharp transition from monolayer to multilayer adsorption is observed. The transition is accompanied by a substantial structural rearrangement in the adlayers immediately at the substrate. Generally it appears that the inclusion of the third dimension in the simulation reveals some important features of the phase transition and of the structure of t…
Dipolar order and disorder phenomena in pure CO and dilute (CO)1−x(Ar)x mixtures physisorbed on graphite
1999
Abstract A detailed heat capacity study has been performed to characterize the properties of pure CO and (CO) 1− x (Ar) x mixture films physisorbed on the basal planes of graphite. The phase diagram of CO monolayers will be presented. At T c =5.18 K a phase transition to a novel low temperature phase is found with head-tail (dipolar) order of the molecules in an orientationally ordered herringbone structure. The phase transition is shown to belong to the 2D Ising universality class with anisotropic interactions between the molecules. Diluting CO weakly with Ar impurities leads to a dramatic destruction of the phase transition. This effect can be quantitatively described by the 2D random fie…
On the commensurate–incommensurate transition in adsorbed monolayers
1999
Abstract A Monte Carlo simulation method is used to study the commensurate–incommensurate phase transition in monolayers and the formation of bilayer films on the (100) face of an fcc crystal. The phase diagram for the system which forms the registered (1×1) and high density incommensurate phases in the monolayer has been determined. It is shown that the registered phase undergoes the transition to a denser incommensurate solid phase when the film density increases. The mechanism of melting of the monolayer film is found to depend on the film density. In particular, the melting of dense incommensurate solid monolayer film is found to be accompanied by the transfer of adsorbed molecules into…
Monte Carlo investigation of head-tail ordering of CO monolayers on graphite
1994
Abstract Heat capacity measurements recently showed that CO physisorbed on graphite undergoes a head-tail ordering transition at roughly 5 K. The present paper is a detailed Monte Carlo study of this phase transition and the ordered state. The simulations are based on an ab initio pair potential and rely crucially on a thorough finite-size scaling study of various quantities. In agreement with experiments we find that the transition belongs to the universality class of the Ising model in two dimensions. We go beyond experimental knowledge by revealing the particular ferrielectric structure of the ground state, and show that the transition is due to the molecule's shape asymmetry rather than…
High-Pressure Raman Study of Fe(IO3)3: Soft-Mode Behavior Driven by Coordination Changes of Iodine Atoms
2020
[EN] We report high-pressure Raman spectroscopy studies of Fe(IO3)(3) up to nearly 21 GPa that have been interpreted with the help of density functional theory calculations, which include the calculation of phonon dispersion curves and elastic constants at different pressures. Zero-pressure Raman-active mode frequencies and their pressure dependences have been determined. Modes have been assigned and correlated to atomic movements with the help of calculations. Interestingly, in the high-frequency region, there are several modes that soften under compression. These modes have been identified as internal vibrations of the IO3 coordination polyhedron. Their unusual behavior is a consequence o…
Crystal Chemistry of CdIn2S4, MgIn2S4, and MnIn2S4 Thiospinels under High Pressure
2012
We report X-ray diffraction measurements in CdIn2S4, MgIn2S4, and MnIn2S4 thiospinels at room temperature and high pressures. The pressure dependences of the structural parameters have been determined and compared to those from theoretical calculations. It is found that the three thiospinels have similar bulk moduli (B-0) between 75 and 80 GPa (B-0' similar to 3). The degree of inversion of these thiospinels has also been determined. The three thiospinels undergo a phase transition toward a defect LiTiO2-type structure above 9.5, 8.3, and 6.8 GPa in CdIn2S4, MgIn2S4, and MnIn2S4, respectively. Interestingly, the low- and high-pressure phases belong to the same symmetry group (Fd-3m), the tr…
Structural and vibrational study of pseudocubic CdIn2Se4 under compression
2014
We report a comprehensive experimental and theoretical study of the structural and vibrational properties of a-CdIn2Se4 under compression. Angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy evidence that this ordered-vacancy compound with pseudocubic structure undergoes a phase transition (7 GPa) toward a disordered rocksalt structure as observed in many other ordered-vacancy compounds. The equation of state and the pressure dependence of the Raman-active modes of this semiconductor have been determined and compared both to ab initio total energy and lattice dynamics calculations and to related compounds. Interestingly, on decreasing pressure, at similar to 2 GPa, CdIn2Se…