Molecular dynamics simulations of oxide memristors: crystal field   effects
  We present molecular-dynamic simulations of memory resistors (memristors) including the crystal field effects on mobile ionic species such as oxygen vacancies appearing during operation of the device. Vacancy distributions show different patterns depending on the ratio of a spatial period of the crystal field to a characteristic radius of the vacancy-vacancy interaction. There are signatures of the orientational order and of spatial voids in the vacancy distributions for some crystal field potentials. The crystal field stabilizes the patterns after they are formed, resulting in a non-volatile switching of the simulated devices. 
S. E. Savel'ev, A. S. Alexandrov, A. M. Bratkovsky, and R. Stanley   Williams
cond-mat.mtrl-sci