Formation of odd-numbered clusters of CO2 adsorbed on nanotube bundles

Simulations show that CO2 adsorbed in the groove sites of carbon nanotubes displays unique quasi-one-dimensional behavior. Clusters containing only odd numbers of molecules are formed at finite CO2 coverages and low temperatures. The molecules are orientationally ordered with respect to the nanotube groove axis and azimuthally ordered in the plane perpendicular to the groove axis. This ordering is a result of a delicate balance between solid-fluid and fluid-fluid forces; the CO2 quadrupole plays a critical role in the cluster formation and orientational ordering.