Tuesday, September 27, 2011

Monday, September 26, 2011

P, D, and G triply periodic minimal surfaces

Finally, I have all three bead models for P, D, and G minimal surfaces corresponding to the simple cubic, diamond-like, and gyroid-like structures, respectively.

A single helical strip

As I discussed in the previous posts, following Chern's construction scheme, I used 16 helical strips to build the overall 2x2x2 gyroical graphitic structure. Each strip contains 8 eight-bead loops, four with blue color and four with purple color as shown in the following photos.

It is interesting note that one can easily create a kink in this helical strip on purpose. A kink in a helix changes the handedness from left to right.

Saturday, September 24, 2011

Gyroidal graphitic structure (2x2x2)

Chern and I have tried to construct this model for more than four years. I have basically made it today. But I may still need to clean all loose ends up. With a rough estimation, about 4500 beads and 100 fishing threads are used. Sixteen long threads (about 3.5 meter long for each strip) are used for making helical strips, and the remaining short threads are used to connect these strips. We can still see many threads in these photos. My wife made an interesting comment that this is really "千頭萬緒" (thousands of strands and loose ends, meaning very complicated) in a tradition chinese phrase.

The following two pictures are taken on my airport extreme.

Sunday, September 18, 2011

Friday, September 16, 2011

Two unit cells of gyroidal graphitic surface (2x1x1)

I found that it is still difficult to identify unambiguously the boundary of gyroidal graphitic structure (GGS) if I don't pay attention to each unit cell carefully from the beginning. So I decided to use the original strategy Chern used to build this structure with helical strips. The photos below show a structure consisting of two unit cells.

In the following photo, I show part of the gyroidal structure that contains only two helical strips. It is interesting to note that one helical strip is right handed and the other one is left handed. But this two-strip unit is still chiral because one of these two strips has to be shifted a half pitch w.r.t. the other strip in order to join them together.

Monday, September 12, 2011


Qian-Rui made these two bead models of EMACs, one with 3 metal cores and the other with 9 cores, last year. The ratio of two types of beads is so small such that the surrounding ligands stop to spiral around the central metal string.

Sunday, September 11, 2011

Bead model of the longest EMAC

Qian-Rui made this bead model of the longest EMAC (Extended Metal Atom Chain) for Prof. J. McGrady (Univ. of Oxford) who is an expert on the electronic structures of this class of molecules and is going to visit our department today. In making this model, Qian-Rui chose 10mm beads for both metal-metal and metal-ligand bonds, and 8mm beads for chemical bonds of surrounding ligands. The pitch of the surrounding ligands is slightly larger than the true molecular structure of this molecule. Only a single nylon cord with about 7 meter long is used for this model.

Here is a photo for the giant structure of this molecule hung in the main lobby of our department.