Ammonia borane structural study by temperature through high-resolution Raman spectroscopy and principal component analysis

The structural change by temperature of the ammonia borane has been studied through Raman spectroscopy and principal components analysis (PCA). Its phase transition, from tetragonal to orthorhombic, was observed at 212 K. In addition, between 99 and 83 K, a zone of structural stability was observed. These behaviors could be observed thanks to the application of the PCA technique to the Raman data. Here, we can find a characteristic Raman signal which can also be associated with the orthorhombic structure. Also using the PCA technique, we have observed two Raman bands in the low frequency region, below 100 cm−1, which could be associated with the lattice vibrational contribution. [Display omitted] •Phase transition of AB at 212 K, from tetragonal to orthorhombic, by means of PCA•Identification of a structural stability zone in orthorhombic phase by means of PCA•Two new low frequency bands of the crystalline lattice observed at low temperatures