Ab initio – phase diagram of NaBH4

Ab-initio crystal structure prediction. A case study: NaBH4

“…Whether it might be experimentally achievable and identified, the monoclinic high energy structure revealed an interesting Na coordination, which eventually represents either a distinct high energy structure, reachable via thermal energy, or a local minimum between two lower minima, namely the tetragonal and the cubic structures. The phonon calculations helped to confirm the lattice stability of the optimized structures and compare the vibrational frequencies with those already reported in literature [12,5]. Clearly, the present study can reveal thermodynamically stable structures regardless whether they are achievable via thermal energy or external pressure.…”

“…However, at finite temperatures, the cubic ðFm3mÞ phase was obtained lower in energy than the tetragonal phase. The phase diagram studies have been recently reported [4,5,[12][13][14][15]. Nevertheless, the discrepancy between the experimental results and a missing theoretical study considering all the phases mentioned above from first-principles urged us to perform an unbiased structural search based on simulated annealing (SA) [16] aiming to find the ground-state structure of NaBH 4 , following the same approach applied for LiBH 4 [17] and MgðBH 4 Þ 2 [18].…”

Pressure-Temperature Phase Relations in Complex Hydrides

“…The results from these two investigations clearly show that the two tetragonal phases are indeed identical, and the phase diagram thus contains only a single tetragonal phase with symmetry c P 1 2 4 . Lee et al [55] have made an attempt to calculate the slope of this phase line using DFT, but the theoretical slope exceeds that found experimentally by a large factor.…”

Structural Characterization of Metal Hydrides for Energy Applications

“…The previous reports suggest that the orthorhombic phase is stable in the pressure range 8.9-30 GPa. Lee et al [170], have studied ab initio structural stability of cubic and tetragonal phases of NaBH 4 up to 30 GPa and 4000 K but an experimental phase diagram is lacking in the current literature in these ranges. A low temperature phase diagram of NaBH 4 was reported by Sundqvist et al [169], in the P-T plane of 0-2 GPa and 100-300 K. In the phase diagram reported by Sundqvist et al [169], tetragonal to orthorhombic phase boundary of NaBH 4 is marked in the range 9-11 GPa.…”

“…Purpose of this study is to explore the thermodynamic properties of metal hydrides [70,71,73,83,170].…”