Solutionso fg allium trihalidesG a X 3 (X = F, Cl, Br,I ) and their ammoniatesi nl iquid ammonia were studied at ambient temperature under autogenousp ressure by multinuclear ( 71 Ga, 35 Cl, 81 Br) NMR spectroscopy.T ou nravel the role of pH, the analysesw ere done both in absence and in presence of ammonium halides, which are employed as mineralizers during ammonoacidic gallium nitride crystal growth. While gallium trifluoride and its ammoniate were found to be too sparingly soluble to give rise to aN MR signal, the spectra of solutions of the heavier halides reveal the presence of as ingle gallium-containing species in all cases. DFT calculations and molecular dynamics simulations suggest the identification of this species as consisting of a [Ga(NH 3 ) 6 ] 3 + cation and up to six surrounding halide anions, resultingi na no verall trend towards negative complex charge. Quantitative 71 Ga NMR studies on saturated solutions of GaCl 3 containing variousa mountso fa dditional NH 4 Cl revealed an ear linear increase of GaCl 3 solubility with mineralizer concentrationo fa bout 0.023 mol GaCl 3 per mol NH 4 Cl at room temperature. These findings reflect the importance of Coulombic shielding fort he inhibition of oligomerization and precipitation processes and help to rationalize both the low solubility of gallium halides in neutral ammonia solution and, in turn, the proliferating effect of the mineralizer during ammonoacidic gallium nitride formation.

We outline a molecular mechanics model for the interaction of gallium and nitride ions ranging from small complexes to nanoparticles and bulk crystals. While the current GaN force fields allow the modelling of either bulk crystals or single ions dispersed in solution, our model covers both and hence paves the way to describing aggregate formation and crystal growth processes from molecular simulations. The key to this is the use of formal  +3 and  −3 charges on the gallium and nitride ions, whilst accounting for the charge transfer in GaN crystals by means of additional potential energy terms. The latter are fitted against experimental data of GaN in the wurtzite structure and benchmarked for the zinc-blende and rock-salt polymorphs. Comparison to quantum chemical references and experiment shows reasonable agreement of structures and formation energy of [GaN] n aggregates, elastic properties of the bulk crystal, the transition pressure of the wurtzite to rock-salt transformation and intrinsic point defects. Furthermore, we demonstrate force field transferability towards the modelling of GaN nanoparticles from simulated annealing runs.

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Catalytic HCO2H dehydrogenation by Ir(Cp*) tetrahydroxy bipyrimidine is influenced not only by the protonation states but also by the involvement of Na+ and the availability of HCO2H as a proton shuttle.

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