Empirical modelling using dummy atoms (EMUDA): an alternative approach for studying "auxetic" structures

Auxetics ( materials or structures) are systems with a negative Poisson's ratio, a property that arises from the way various geometric features in the structure ( or internal structure in the case of materials) deform when subjected to uniaxial loads. Such systems are normally studied by examining the behaviour of idealised representations of structures, which deform in a controlled fashion ( e. g. deforming solely through hinging or stretching). Methods used for the analysis typically involve construction of real physical macro-models and/or derivation of analytical expressions for the mechanical properties. This paper proposes an alternative method for analysing such structures whereby idealised "hinging" or "stretching" structures are constructed within a molecular modelling environment using dummy atoms and examined using standard molecular mechanics techniques. We will show that this methodology of "empirical modelling using dummy atoms" (EMUDA) successfully reproduces the known properties of 2D conventional and auxetic hexagonal honeycombs hence confirming the suitability of this technique for studying auxetic structures.