Atoms are spaced periodically in one direction on a surface perpendicular to a quasicrystals 10-fold rotational axis. But at right angles they are spaced in a Fibonacci sequence, in which the ratio of short to long spacings is an irrational number like that of the Golden Mean. Friction is eight times greater in the periodic direction than in the aperiodic direction.
The Da Vinci Code, the best selling novel and soon-to-be-blockbuster film, may also be linked some day to the solving of a scientific mystery as old as Leonardo Da Vinci himself — friction. A collaboration of scientists from Lawrence Berkeley National Laboratory (Berkeley Lab) and the Ames Laboratory at Iowa State University have used Da Vinci’s principles of friction and the geometric oddities known as quasicrystals to open a new pathway towards a better understanding of friction at the atomic level.
In a paper published in the August 26 issue of the journal Science, a research collaboration led by Miquel Salmeron, a physicist with Berkeley Lab’s Materials Sciences Division, reports on the first study to measure the frictional effects of periodicity in a crystalline lattice. Using a combined Atomic Force Microscope (AFM) and Scanning Tunneling Microscope (STM), the researchers showed that friction along the surface of a quasicrystal in the direction of a periodic geometric configuration is about eight times greater than in the direction where the geometric configuration is aperiodic (without regularity).
Geometric periodicity was confirmed via rows of atoms that formed a Fibonacci sequence, a numerical pattern often observed in quasicrystals — and which was one of the clues to solving the Da Vinci code in the novel by Dan Brown.
Lynn Yarris | EurekAlert!
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