About crystal structures of packed double-ions or linear molecules in a FCC lattice

作者：Maaskant W J A^*

来源：Physica B: Condensed Matter , 2012, 407(3): 509-514.

DOI：10.1016/j.physb.2011.11.025

• Inorganic
• FeS2 (pyrite)
• N-2
• CO2
• Electrostatic quadrupole-quadrupole interaction

We derive the crystal-structures of FeS2 (pyrite), N-2 and CO2 and similar species, where the double-ions or molecules can be regarded as linear entities, placed in a face-centred cubic (FCC) lattice. The interaction between two of these elongation directions is determined by three constants. A minimum is reached by orienting the elongations of neighbouring ions or molecules in a perpendicular way, which points to electrostatic quadrupole-quadrupole interactions and which has been noted before in ortho-hydrogen and para-deuterium. For several points in the Brillouin zone the interaction is calculated. Especially the X-points are of interest and determine the space group Pa (3) over bar, which is a subgroup of Fm (3) over barm, the original group of the fcc lattice. We derive also an alternative setting for Pa (3) over bar. The conclusion is made that for all these compounds with a Pa (3) over bar structure an electrostatic quadrupole-quadrupole interaction is present.

• 出版日期2012-2-1