  A three-dimensional phase-field approach to martensitic transformations that
uses reaction pathways in place of a Landau potential is introduced and applied
to a model of Fe3Ni. Pathway branching involves an unbounded set of variants
through duplication and rotations by the rotation point groups of the austenite
and martensite phases. Path properties, including potential energy and elastic
tensors, are calibrated by molecular statics. Acoustic waves are dealt with via
a splitting technique between elastic and dissipative behaviors in a
large-deformation framework. The sole free parameter of the model is the
damping coefficient associated to transformations, tuned by comparisons with
molecular dynamics simulations. Good quantitative agreement is then obtained
between both methods.
