Orthohexagonal
From Online Dictionary of Crystallography
Orthohexagonal (Fr). Orthohexagonalen (Ge). Ortoesagonale (It). 直方六方 (Ja). Ortohexagonal (Sp).
The hexagonal lattice is frequently referred to an orthorhombic C-centred cell called orthohexagonal, whose volume is twice that of the conventional P cell. Three choices of the orthohexagonal cell are possible:
- C_{1}, basis vectors change a, a+2b, c;
- C_{2}, basis vectors change a+b, -a+b, c;
- C_{3}, basis vectors change b, -2a-b, c.
The hexagonal symmetry is reflected in the metric specialisation of the orthohexagonal cell, which has b = a3^{1/2}. As a consequence, an orthorhombic crystal with conventional cell of type oC and b = a ratio close to 3^{1/2} has a pseudo-hexagonal lattice.
See also
- Chapter 1.5 of International Tables for Crystallography, Volume A, 6th edition