4. TCE Adsorption on CNT: Results from Molecular Modeling
To understand the relative affinity of TCE to CNTs, all-atom molecular dynamics simulations,
employing the force field parameters in our previous work [69,70], were carried out on single walled
carbon nanotubes (SWCNTs) and graphite sheets. The SWCNTs have a diameter of 2 nm and length
between 8 and 12 nm. The graphite is composed of four graphene sheets with system size varying from
5x5 nm2 to 15x15 nm2 Simulations with a time integral of 1 fs, with equilibration of 5 ns and a
minimum production run of 1 ns carried out. Initial distribution of TCE molecules on both substrates
were random, and a short run of 10 ps with soft potential was done to minimize any overlaps. Both the
CNT and graphite systems were fixed.
The mean-squared displacement (MSD) curves for both graphite and SWCNTs (Figure 11)
show higher TCE mobility on the graphite surface. In the presence of water (data not shown),
both mobilities decrease. For the current systems, since only van der Waals forces contribute to the
adsorption of TCE on graphite and CNT, and the force fields are similar for both, curvature effects
(as opposed to charge transfer and induced polarity), are expected to be the main reason for higher
mobility of TCE on graphite.