An Old Dog with New Tricks – Additions to the Cesium Lithium Chloride System: Cs3Li2Cl5 and the Hydrated Cs3LiCl4·4H2O.

The CsCl/LiCl system has been studied for over a century now. Numerous phases have been predicted – only three have hitherto been found. We present the synthesis and single‐crystal structure of the cesium lithium pentachloride Cs3Li2Cl5, predicted earlier but with a different structure. The anhydrous new phase readily reacts to Cs3LiCl4·4H2O in air. The tetrahydrate can also be obtained through the simplest, most inexpensive and green synthesis possible: an immediate, room‐temperature mechanosynthesis from only CsCl and LiCl (3:1) in air. Differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA), as well as in situ temperature‐dependent powder X‐ray diffraction studies on this second ever reported ternary alkali chloride hydrate allowed for a revision of the CsCl/LiCl phase diagram. Density of states and total energy calculations further elucidate the new alkali chlorides and update the relative stability of previous structure predictions. [ABSTRACT FROM AUTHOR]