The stable formation of defects and nano-clusters in lithium fluoride by high energy ion bombardment has been widely reported in the literature [1-3]. In contrast, only a few articles have been published on the effect of low energy (< 200 eV) ion bombardment on defect and nano-cluster formation. Ion beam assistance during the deposition process is one of the methods to generate colour centres and nano-clusters in lithium fluoride thin films [2]. In this work, we present a model to describe the physical processes that underlie the formation of primary defects (F colour centres, anion vacancies occupied by electrons)[3] and lithium nano-clusters (Li colloids)[4], during the low energy assistance by Xe ions of thermal evaporated LiF thin films. The model is a combination of the physics on which the program SRIM (The Stopping and Range of Ions in Matter)[5] is based, and the cylindrical spike thermal model [6, 7].