Second-nearest-neighbor effects on the NMR shielding of N in P3N5 and hexagonal BN

NMR shieldings calculated at the central N atom in models for solid P3N5 and BN are strongly influenced by the presence of additional N atoms in second-nearest-neighbour positions. For P3N5 such effects are deshielding while for hexagonal BN they are shielding. This indicates both that accurate calculation of N shieldings in solids will require large cluster models and that such shieldings will give information on mid-range order within the material.