The fluorine ion mobility in Pb0.8M0.2F2 and Pb0.75M0.2K0.05F1.95 (M = Ca, Ba) solid solutions
with fluorite structure under normal conditions was calculated using classical molecular dynamics.
It was shown that isovalent substitution of lead atoms by calcium atoms in a lead fluoride crystal
increases the mobility of fluorine ions, while a similar substitution by barium atoms decreases it. Heterovalent substitution Pb → K naturally increases the fluorine ion mobility in the Pb0.75Ca0.2K0.05F1.95
and Pb0.75Ba0.2K0.05F1.95 solid solutions.