Density functional theory (DFT) calculations at generalized gradient approximation (GGA) level were performed to interpret experimental IR and Raman vibrational spectra, to assign B-11-NMR chemical shifts, and to calculate the structure of the tetrahydroxyborate sodalite Na-8[AlSiO4](6)(B(OH)(4))(2). Full optimization of the intercalated compound gave the following structural parameters of B(OH)(4)(-): B-O-B (105.3-115.3 degrees) and B-O-H (111.5-115.4 degrees) angles, B-O (1.476 angstrom, 1.491 angstrom) and O-H (0.98 angstrom) distances. The calculated normal modes were assigned to experimental IR and Raman spectra. In general, close agreement between theory and experiment was obtained. The mean absolute deviation (MAD) is below 11 cm(-1). We also calculate the thermodynamical stability of Na-8[AlSiO4](6)(B(OH)(4))(2) with respect to Na-8[AlSiO4](6)(BH4)(2) in the context of the tetrahydroborate hydration reaction.