  In this paper we infer the structure of Pd40Ni40P20 from experimental
diffraction data and ab initio interactions using Force Enhanced Atomic
Refinement (FEAR). Our model accurately reproduces known experimental
signatures of the system and is more efficient than conventional melt-quench
schemes. We critically evaluate the local order, carry out detailed comparisons
to extended X-ray absorption fine structure (EXAFS) experiments and also
discuss the electronic structure. We thoroughly explore the lattice dynamics of
the system, and describe a vibrational localized-to-extended transition and
discuss the special role of P dynamics. At low energies P is fully contributing
to extended modes, but at higher frequencies executes local motion reminiscent
of a rattler inside a cage of metal atoms. These highly localized vibrational
states suggest a possible utility of these materials for thermoelectric
applications.
