Auxetics at the Molecular Level: A Negative Poisson's Ratio in Molecular Rods

N. Pour et al, "Auxetics at the Molecular Level: A Negative Poisson's Ratio in Molecular Rods"

Angew. Chem. Int. Ed. 45, 5981 (2006)

Most materials become thinner when they are pulled longitudinally, and thicker when compressed. However, auxetic materials have just the opposite behavior--while this might seem counterintuitive, in fact foams, certain crystals (along special axes), and the exotic forms of matter found in white dwarfs all have this property. In this paper, the authors perform (AM1, various DFT, and MP2) calculations to demonstrate this type of behavior on the nanoscale for prismane-like rods. While more of a theoretical curiosity at this point, the authors hope this will stimulate the syntheses of these types of materials.

A Four-position Chlorophyll-a molecular switch

Violeta Iancu and Saw-Wai Hla, "Realizing a Four-Step Molecular Switch in Scanning Tunneling Microscope Manipulation of Single Chlorophyll-a Molecules"

cond-mat/0609077

This paper combines a lot of things I like reading about: chlorophyll, STM-manipulation of molecules, and semi-empirical calculations. Basically the title says it all: you can use inelastic tunneling spectroscopy (IETS) to move the phytyl tail around into 4 distinct positions. The pictures are quite nice too, thanks to the PM3 calculations.