In the snapshots below, electrons are shown as spheres of varying size. Spin is indicated by color: up spins are red, down spins are blue, and paired pairs are grey.
eFF can describe intermolecular interactions between hydrogen molecules, shown compressed in a solid to a density of 0.5 g/cc. Finite temperature equations of state agree well with those obtained from diamond anvil experiments.
eFF can describe two-electron three-center bonds of the sort found in diborane, as well as more traditional covalent and ionic bonds in compounds such as methane and lithium hydride.
We use eFF to study the relaxation of core-ionized molecules, which may play a role in surface etching by photons or electrons. We observe the characteristic steps of the Auger process: one valence electron fills the core hole, while another one is ejected. This calculation, with 75 electrons (0.0021 sec/step), took 3.5 minutes (105 steps = 100 fs / 0.001 fs) to complete.
Here we use eFF to simulate diamond etching by a dense hydrogen plasma. This calculation, with 3,792 electrons (2.9 sec/step), took 3.4 days (105 steps = 2 ps / 0.020 fs) to complete.
We are interested in using eFF to study radiation damage in materials, e.g. the effects of high energy protons on beryllium, a candidate first-wall material for the ITER fusion reactor. This calculation, with 88,704 electrons (78 sec/step), took 1.8 days (2000 steps = 100 fs / 0.050 fs) to complete.