PbFCl-type derivatives

If we compare a series of compounds with the same tetrahedron layer, such as ThNCl, ThNBr and ThNI, we notice that the lattice constant a remains practically constant, while the value of c increases and the layer character becomes more pronounced. It follows from Table 139 that the layer character becomes more pronounced in rare-earth series, LnOCl or LnOBr, on going from La to a heavier rare-earth atom. For MFX phases Beck [983] derived from electrostatic calculations that with smaller cations M as well as with larger anions X c/a will increase. The limiting phase with r(X) r(F) has c/a — 1.5 which roughly corresponds to the FeSi2 type. Symmetry reduction transforms the FeSi2 type to the PbFCl type with c/a = n/2. 

PbFCl-type ThN(NH2) is unknown, but the yellow imide Th(NH)2 has a layer structure derived from a-Th3N4 (Table 200, Appendix). 

The structure derived from the PbFCl type structure a - V2 c = 2c , where and c are the PbFCl parameters... 

PbFCl-type (QFPb) s Fc2As-type (FeFeAs) derivative... 

Isothermal bulk modulus (GPa) and its pressure derivative K for ambient pressure phases of lanthanide and actinide compounds of the Fe2As and PbFCl structure types. 

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