  We present a density functional theory analysis of nitrogen-vacancy (NV)
centers in diamond which are located in the vicinity of extended defects,
namely intrinsic stacking faults (ISF), extrinsic stacking faults (ESF), and
coherent twin boundaries (CTB) on \{111\} planes in diamond crystals. Several
sites for NV centers close to the extended defects are energetically preferred
with respect to the bulk crystal. This indicates that NV centers may be
enriched at extended defects. We report the hyperfine structure (HFS) and
zero-field splitting (ZFS) parameters of the NV centers at the extended defects
which typically deviate by about 10\% but in some cases up to 90\% from their
bulk values. Furthermore, we find that the influence of the extended defects on
the NV centers is of short range: NV centers that are about three double layers
(corresponding to $\sim6$ $\mathring{A}$ away from defect planes already show
bulk-like behavior.
