[UO₂(NH₃)₅]Br₂·NH₃: synthesis, crystal structure, and speciation in liquid ammonia solution by first-principles molecular dynamics simulations

Abstract

Additional Computational Details PCM and NBO calculationsStarting from the gas-phase BLYP/SDD/6-311+G** equilibrium structures, [UO 2 L 5 ] 2+ (L = H 2 O, NH 3 ) were re-optimised using the polarisable continuum model in its integral equation formalism (IEF-PCM), 1 as implemented in Gaussian 09. 2 For L = H 2 O, standard solvent parameters of water were used, for ammonia we employed the static dielectric constant of liquid ammonia at 20ºC ( = 16.6), 3 the same dynamic dielectric constant as water, 4 and a solvent radius of 2.5 Å. 5 Natural bond orbital analyses 6 employed the Gaussian NBO version 3.1 as implemented in Gaussian 09. CPMD simulationsThe same methods and basis sets as in our previous studies of uranyl complexes 7 were employed. Car-Parrinello molecular dynamics (CPMD) 8 simulations were performed using the BLYP functional 9 and norm-conserving pseudopotentials that had been generated according to the Troullier and Martins procedure 10 and transformed into the Kleinman-Bylander form. 11 For uranium, the semicore (or small-core) pseudopotential was employed that had been generated and validated in reference 12. Periodic boundary conditions were imposed using cubic supercells with a lattice contant of 13.22 Å. Kohn-Sham orbitals were expanded in plane waves at the -point up to a kinetic energy cutoff of 80 Ry. Simulations were performed in the NVT ensemble using a single Nosé-Hoover thermostat set to 300 K (frequency 1800 cm 1 ), a fictitious electronic mass of 600 a.u., and a time step of 0.121 fs. The boxes contained uranyl and and a total of 42 ammonia molecules, affording a density of 0.71. The system has two positive charges, neutralised by a uniform background charge. In order to maintain the time step, hydrogen was substituted with deuterium. Long-range electrostatic interactions were treated with the Ewald method. No electrostatic decoupling between replicated cells was included.Constrained CPMD simulations were performed along a predefined reaction coordinate  (a single U-N bond distance r), starting from the respective mean values for the five-coordinate minumum in gas and solution (as obtained from the unconstrained simulations. Changes in the Helmholtz free energes were evaluated by pointwise thermodynamic integration 13 of the mean constraint force f along this coordinate via      A ab =  a b f()d (1). Electronic Supplementary Material (ESI) for Dalton Transactions. This journal is

Reactions of ThX4 (X=F, Cl, Br, I) with Liquid Ammonia‐Crystal Structures and a Theoretical Study of Ammine Thorium(IV) Halide Ammoniates

“…These hydrogen bonds for the different decaammine thorium(IV) halides are in good agreement with known N−H⋅⋅⋅ X ( X= Cl, Br, I) hydrogen bonds for example in [Co(NH 3 ) 6 ]Cl 2 (3.601 Å, T =294 K), [Co(NH 3 ) 6 ]Br(S 2 O 3 ) ⋅ H 2 O (3.509(4) to 3.539(3) Å, T =295 K) or [CoCO 3 (NH 3 ) 5 ]Br ⋅ H 2 O (3.41 to 3.63 Å), or [Co(NH 3 ) 6 ]I 3 (3.902 Å, T =298 K) [10,31‐36] …”

Crystal structure of [UO2(NH3)5]NO3·NH3

“…Br 2 ÁNH 3 , U-O distances in the range 1.768 (2) to 1.771 (3) Å were reported (Woidy et al, 2012(Woidy et al, , 2015b; these are shortened by ca 0.1 Å compared to the uranyl ion presented here.…”

Dissolved Intermediates in Ammonothermal Crystal Growth: Stepwise Condensation of [Ga(NH2)4]− toward GaN

“…For the calculations, the ωB97xD functional by Head-Gordon and basis sets from the def2-family by Weigend and Ahlrichs were employed. Numerical integrations were performed on an ultrafine grid, and solvent effects were included by using a PCM model as implemented in the Gaussian package and employing the same solvent parameters for ammonia as described elsewhere . Energy-optimization of molecular structures and harmonic vibrational analyses were carried out at the PCM-ωB97xD/def2-tzvp level without symmetry constraints, and magnetic shieldings were then calculated for the final geometries at the PCM-ωB97xD/def2-tzvpp level.…”