The interface between physics, chemistry (and materials science) can be a fascinating one. Here I show a carbon nanotorus, devised by physicists[1] a few years ago. It is a theoretical species, and was predicted to have a colossal paramagnetic moment.
Carbon nanotorus. Click for 3D.
At 1364 carbon atoms, it is a little too big to calculate any of its expected chiroptical properties (the torus twists in a helical manner, and so is chiral). So we can only speculate whether e.g. its optical rotation would also be colossal! Or, what applications such a nanodevice might have. This post, by the way, was induced by seeing Steve Bachrach’s fascinating exploration
of chiral nanohoops.
References
- L. Liu, G. Guo, C. Jayanthi, and S. Wu, "Colossal Paramagnetic Moments in Metallic Carbon Nanotori", Physical Review Letters, vol. 88, 2002. http://dx.doi.org/10.1103/PhysRevLett.88.217206
Tags: chiroptical, metallic carbon, nanotorus, Steve Bachrach
Perhaps some semi-empirics can give a glimpse at the chiroptical properties? ( ZINDO/S ) Maybe even PPP ?
The original magnetic properties were probed using π-orbital tight-binding theory
(which is related to PPP theory). Chiroptical properties tend to focus on time-dependent density functional implementations (DOI: 10.1371/journal.pone.0010617
; it might be that no-one has explored chiroptical properties using tight binding, π-only theories.
Tight-binding is the physicist’s extended hueckel theory, yes.
). I know the ORCA program can do CIS with ZINDO/S, but not PPP. Dont even know if there is any freely available program that can still do (TD-)PPP.
We have a TD-PPP (full RPA) code in our group, it gives nice (qualitative) results (eg. for large organic systems DOI: 10.1039/b925334c
I would give it a try, but I dont see how I can get a structure.
If you follow the procedure outlined at this post
, you will be able to acquire access to the coordinates of the nanotorus. These may need further optimisation, but in any case might suffice to explore a TD-PPP calculation for this species?
[...] and with the current interest in the magnetic properties of graphene-like objects (see also this blog post and also the helical metal wire) such molecules can only help to excite our [...]