MOLECULE -- please stay -- SOLVED!
The solution was to add one or more half rings to wide tubes.
Wide tube, with an attached half ring of carbon atoms shown at left.
Discussion of testing several attached configurations
in Omri's thesis. Unless an entire ring is added (where there is clear evidence of a decrease in frequency with an increase in weight), symmetry between
x and z directions is broken, so we have less statistics for each case, as behavior can differ in the perpendicular directions.
Considerations of a possible increase in frequency due
the contact area between the added rings and the nanotube and a resultant change in elasticity.