In the mixed crystal system CdxSn1-xTe, the transition from a ten-elec
tron (x=0) to an eight-electron system (x=1) is realized, which is acc
ompanied by a change in the crystal structure from rocksalt (SnTe) to
zincblende (CdTe). The structure and lattice constants of solid soluti
ons, grown (in part under high pressure) for nearly the whole mixing r
ange, are known. We use norm-conserving pseudopotentials in connection
with the local density and virtual crystal approximation for ab initi
o calculations of the stable crystal structure and the lattice constan
t in dependence on the composition x of the system. Our calculated res
ults confirm Vegard's rule and give a crossover from rocksalt to zincb
lende at about x=0.9 in accordance with experimental data. The crossov
er is accompanied by a change in the binding character, which can be s
een in a change of the electronic charge density.