| Structural type | A3', B8_1 |
| Common name | A3' – alpha-lanthanum, B81 – nickel arsenide |
| Definition | close-packed ABAC=ch structure |
| Prototype | A3' – α-La, B81 – NiAs |
| Pearson symbol | hP4 |
| Space group | 194 P63/mmc D6h4 |
| Chemical formula | AB |
| Bonding | metallic, ionic |
| Atomic positions |
A (2a) 0 0 0 (marked by C)
B (2c) 1/3 2/3 1/4 (marked by S) |
| Coordination | 6+6 (12co for A and 12aco for B) |
| Sublattices | A – sh, B – hcp |
| PDB files | A3p, B8_1 |
| Parameters | c/a (A=B and c/2a≈1.63 for A3', c/a<1.6 for B81) |
| Special cases | ideal packing for c/2a=sqrt(8/3)≈1.63
maximum Madelung constant M=1.732 for c/2a≈1.77 |
| Substances | A3' – some rare-earth metals (see the table below),
B81 – transition metals + V-VI (see the table below) |