Condensed Matter Theory

& Computer Simulations

 

adsorption in nanopores

Adsorption within pores and on surfaces occurs because of the attractive potential provided by the adsorbent. If the attraction is too weak, however, adsorption does not occur to any significant extent. A criterion for such adsorption, at zero temperature, of the quantum gases 4He and H2 is expressed as a relationship between a threshold value of the well-depth (D) of the adsorption potential and the hard-core diameter (σ) of the gas-surface pair potential. Read more...Thresholds.htmlshapeimage_1_link_0
Water wets... or not? A wetting transition occurs when the contact angle of a liquid drop on a surface changes from a nonzero value to zero. Such a transition has never been observed for water on any solid surface. We predicted the value of the temperature Tw at which the transition should occur for water on graphite to be in the range 350-500K. Read more... water.htmlshapeimage_2_link_0

  1. BulletBundles of carbon nanotubes have many sites for adsorption. The grooves are very attractive and accessible to all species. Read more...

  1. BulletRelaxation of the substrate.

Substrates can have an active role in the final equilibrium state of the adsorbates.

3He is a not self-bound gas in 1D or 2D, because it is a fermion  of very weak atomic interaction, and also very light. However it is a liquid within a thin  slit pore or narrow nanotube. The condensation happens thanks to the relaxation of the substrate, and it would NOT occur if the substrate were rigid. Reason: the fluid exploits large gas-substrate energy scale, a small change in the radius of a nanotube or separation of a slit pore upon adsorption of 3He may change dramatically the final state of the system.  Read more...

  1. BulletXenon in Buckyballs

Xe adsorption on a C60 monolayer on Ag(111). The most attractive sites located in the threefold hollows between the C60 molecules, forming a honeycomb array. These attractive sites are filled first, followed by adsorption in two types of secondary sites, where a competition exists due to steric hindrance. Read more...