  Particle based methods such as the Discrete Element Method and the Lattice
Spring Method may be used for describing the behaviour of isotropic linear
elastic materials. However, the common bond models employed to describe the
interaction between particles restrict the range of Poisson's ratio that can be
represented. In this paper, to overcome the restriction, a modified bond model
that includes the coupling of shear strain energy of neighbouring bonds is
proposed. The coupling is described by a multi-bond term that enables the model
to distinguish between shear deformations and rigid-body rotations. The
positive definiteness of the strain energy function of the modified bond model
is verified. To validate the model, uniaxial tension, pure shear, pure bending
and cantilever bending tests are performed. Comparison of the particle
displacements with continuum mechanics solution demonstrates the ability of the
model to describe the behaviour of isotropic linear elastic material for values
of Poisson's ratio in the range $0 \leq \nu < 0.5$.
