Postdesorption Fragmentation of Tetradecane in Atom-Probe Tomography Simulated by DFT.

Atom probe tomography (APT) can measure the composition of complex materials with up to atomic resolution by ionizing and desorbing atomic and molecular fragments at high electric fields from a surface. In molecular structures, the desorption products are often whole molecular ions, which can fragment on the way to the detector, providing insight into their atomic composition. We study the postdesorption fragmentation of n-tetradecane as an example of organic molecules and compare it to experimental APT results. We find that strong electric fields cause the monocation to fragment asymmetrically, preferentially producing ethyl and propyl carbocations. The dication of n-tetradecane was found to be only metastable even in the absence of an external field and was found to fragment easily in an applied field.