Grooves molecular motion

Simulations of self-diffusion have been reviewed recently [60]. In addition to molecular motion on flat surfaces (including those with atomic roughness), selfdiffusion constants have been evaluated for atoms adsorbed on surfaces with comers (as in pores with rectangular cross sections or on grooved surfaces) and with steps. In these systems, a deep nearly one-dimensional potential well occurs in the model gas-surface energy at the comers. Atoms adsorbed in this well are essentially localized in one-dimension, which means that self-diffusion hardly occurs in the directions perpendicular to the comer. 

M. J. Bojan and W. A. Steele, Computer Simulation of Physisorbed Kr on a Heterogeneous Surface, Langmuir 5 (1988) 625-633 Molecular Motion in Krypton Films Physisorbed on a Grooved Surface, Berichte Bunsenges Phys. Chem. 94 (1990) 300-306. 

Figure 9-19 Phonon dispersion relation (angular frequency vs. relative wave vector) for the three-stripe phase of CH4 on the external surface of a bundle. LI, L2, and L3 are longitudinal branches, i.e., molecular motion parallel to the groove. The dotted curve is the result for a ID adsorbate at the same density. The remaining curves correspond to the dispersion relation of transverse modes. (Adapted from Ref. [89].)...

In free molecular flow, if gaseous conductance were not independent of the flow direction, a perpetual-motion machine could be constmcted by connecting two large volumes by a pair of identical ducts having a turbine in front of one of the ducts. A duct that has asymmetricaUy shaped grooves on its waU surface could alter the probabUity of molecular passage in such a way that for a tube of equal entrance and exit areas, the probabUity of passage would be made directional. 

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