Coulomb’s law of electrostatic forces says that particles with the same electric charge repulse each other, but opposites attract. This explains why plastic bags sometimes stick to your clothes or why long hair crackles when woolen jumpers come out.
In the world of atoms and molecules, electrostatic forces are important because they determine many of the chemical properties we observe in substances, for example crystal structure or how well something dissolves in water.
The standard method to image the distribution of electrostatic forces around molecules, called kelvin probe force microscopy, is useful to chemists and physicists, but it comes with many shortcomings.
Pavel Jelínek and his colleagues from the Nanosurf team at the Institute of Physics of the Czech Academy of Sciences, decided to look for improvements. Together with his team, Jelínek devised a new method based on the idea that the electrostatic field creates a distortion in high-resolution microscopy images of molecules. The distortion will depend on the type of tip used in the probe taking the image. The difference between two images of the same molecule acquired with different probe tips shows the distribution of the electrostatic field.
Two images of the same hydrocarbon TOAT molecule, taken with a CO probe tip (top) and a Xe-modified tip (bottom). The distortion shows the molecule’s electrostatic field.
Jelínek and the Nanosurf team used the computing resources provided by MetaCentrum (the Czech arm of the EGI Community) for the simulations necessary confirm the validity of the new method. MetaCentrum provided an optimal platform for such extensive simulations including a uniform environment for the simulations, technical support for optimising codes and parallel computing on many CPUs.
Hapala et al. 2016 Mapping the electrostatic force field of single molecules from high-resolution scanning probe images. Nature Communications doi:10.1038/ncomms11560