CS2CAH4, A NEW HYDRIDE - THE ATOMIC VOLUM E OF HYDROGEN AS A CRITERION TO CHECK CRYSTAL-STRUCTURE AND COMPOSITION

According to the investigations of Park, Pezat, and Darriet CsCaH3 cry stallizes in the GdFeO3 structure type. As the resulting atomic volume of hydrogen is too small for a ionic hydride a re-examination of the crystal structure has been carried out. The results of our investigati ons show that the compound under discussion is actually Cs2CaH4. It cr ystallizes in the K2NiF4 structure type with the expected atomic volum e for hydrogen. The complete crystal structure has successfully been d etermined by a neutron diffraction experiment on the deuteride Cs2CaD4 .