  The primary factors controlling defect stability in phase-field crystal (PFC)
models are examined, with illustrative examples involving several existing
variations of the model. Guidelines are presented for constructing models with
stable defect structures that maintain high numerical efficiency. The general
framework combines both long-range elastic fields and basic features of
atomic-level core structures, with defect dynamics operable over diffusive time
scales. Fundamental elements of the resulting defect physics are characterized
for the case of fcc crystals. Stacking faults and split Shockley partial
dislocations are stabilized for the first time within the PFC formalism, and
various properties of associated defect structures are characterized. These
include the dissociation width of perfect edge and screw dislocations, the
effect of applied stresses on dissociation, Peierls strains for glide, and
dynamic contraction of gliding pairs of partials. Our results in general are
shown to compare favorably with continuum elastic theories and experimental
findings.
