What Is The Crystal Structure Of Americium(III) Chloride?

Americium(III) chloride (AmCl3) belongs to the class of transition metal halides and has a crystalline structure that is dependent on temperature.

At room temperature, AmCl3 adopts a hexagonal close-packed (hcp) crystal lattice structure with space group P63/mmc. In this structure, each americium ion is surrounded by nine chloride ions, forming a distorted tricapped trigonal prism coordination geometry. The chloride ions act as bridging ligands, connecting neighboring americium ions.

As the temperature increases above 825 °C, AmCl3 undergoes a phase transition to a face-centered cubic (fcc) structure with space group Fm-3m. In this structure, each americium ion is again surrounded by nine chloride ions, but they form a more regular octahedral geometry. The chloride ions still act as bridging ligands between the americium ions.

It's worth noting that due to the high radioactivity of americium, studying its crystal structure is challenging and limited information is available.