The role of fluid-wall interactions on confined liquid diffusion using Mori theory

Abstract

The dynamics of fluid confined in a nano-channel with smooth walls have been studied through velocity autocorrelation function within the memory function approach by incorporating the atomic level interactions of fluid with the confining wall. Expressions for the second and fourth sum rules of velocity autocorrelation have been derived for nano-channel which involves fluid-fluid and fluid-wall interactions. These expressions, in addition, involve pair correlation function and density profiles. The numerical contributions of fluid-wall interaction to sum rules are found to play a very significant role, specifically at smaller channel width. Results obtained for velocity autocorrelation and self-diffusion coefficient of a fluid confined to different widths of the nanochannel have been compared with the computer simulation results. The comparison shows a good agreement except when the width of the channel is of the order of two atomic diameters, where it becomes difficult to estimate sum rules involving the triplet correlation's contribution.

Nonequilibrium molecular dynamics simulations of nanoconfined fluids at solid-liquid interfaces

“…2(b), the amplitude of the density oscillations rapidly decays while approaching the bulk volume of the fluid. 18,23,51,58 It is noteworthy that the values of the density at the near-constant plateaus in the center of the channel are slightly, but noticeably, different for the hydrophilic and hydrophobic cases. This is a manifestation of the Kelvin shift of the bulk coexistence curve, which occurs due to the spatial confinement of the fluid, 59 reflecting the higher degree of effective confinement in the hydrophobic case due to the repulsive wall layer.…”

Thermal, caloric and transport properties of the Lennard–Jones truncated and shifted fluid in the adsorbed layers at dispersive solid walls

“…Less is known on thermodynamic and transport properties of the fluid in the adsorbed layers [15]. MD simulations have been used before to study the following properties of simple fluids adsorbed to walls: self-diffusivity [8,[15][16][17][18][19][20][21][22][23][24], thermal conductivity [23,[25][26][27][28][29], and shear viscosity [23,29,30]. In most of these studies, fluid properties were determined as mean values in nanochannels that were so small that the adsorbed layers on both walls interfered [1,5,6,13,16,31,32].…”

Analysis on the energetics, magnetism and electronic properties in a 45° ZnO grain boundary doped with Gd

“…The varied atomic co-ordination manifesting as under- or over-coordination of atoms in a GB creates dangling bonds that can facilitate formation of native defects and segregation of dopants. 8 As GBs with different angles affects the material properties in different ways, 30 ZnO GBs with low and high angles 31 characterized by short and long periodicity were investigated previously. For example, Sato et al 32 obtained a wide variety of GB atomic structures in ZnO solely by changing the relative orientation of the GB planes.…”

“…Both stoichiometric and non-stoichiometric GBs have been found to significantly affect the properties of ZnO materials, such as producing distinct occupied and unoccupied levels, with changes in the coordination and concentration of O atoms, which in turn produces varistor effect in the undoped conditions. 9 Recently, we have also demonstrated FM in ZnO GB in presence of cation vacancies, 8 wherein FM originates from the localized holes forming triplet states, thus giving rise to a stable magnetic ground state. 10 This magnetic phenomenon originates from the p band, rather than the d band (in which case it is referred to as the d 0 FM.…”

“… 1 While GaAs and GaN based DMS were the subject of most prior investigations in this field, 2 the focus has recently shifted to ZnO, as it exhibits room temperature ferromagnetism (RTFM) in presence of transition metals (TMs) 3 and rare earth (RE) elements. 4–7,19 The existence of intrinsic defects, such as dislocations, grain boundaries (GBs), and vacancies in ZnO also assists in inducing magnetic properties, 8 and the ferromagnetic coupling strength is increased when defect-dopant complexes are present in the material. 3 In particular, ZnO GB can play a role in the ferromagnetism (FM) of ZnO.…”