[1][2] In particular, the lattice constants of the analogous lanthanum and actinium compounds differ by only a few percent.
The former reaction is carried out at room temperature, by adding hydrofluoric acid to a solution containing actinium ions.
In the latter method, actinium metal is treated with hydrogen fluoride vapors at 700 °C in an all-platinum setup.
However, in contrast to the oxyfluoride, the oxychloride could well be synthesized by igniting a solution of actinium trichloride in hydrochloric acid with ammonia.
It may possibly be produced by acting with a mixture of hydrogen sulfide and carbon disulfide on actinium oxide at 1000 °C.