  We perform ab initio density functional calculations to study the flow of
water, methanol and dimethyl ether through nanotubes of carbon and boron
nitride with different diameters and chiralities. The liquids we choose are
important solvents, with water and methanol being polar and dimethyl ether
being non-polar. In terms of activation barriers for liquid transport, we find
the molecular-level drag to decrease with decreasing nanotube diameter, but to
be rather independent of the chiral index. We also find molecules with higher
polarity to experience higher drag during the flow. Counter-intuitively, we
find the drag for water in boron nitride nanotubes not to exceed that in carbon
nanotubes due to frustration in competing long-range Coulomb interactions.
