Biomedical subjects

Oliver Hochrein

Publications and source records attributed to Oliver Hochrein.

2 recordsLinked to original sources

PubMed2007

Control of channel shapes in a microporous manganese(II)-borophosphate framework by variation of size and shape of organic template cations.

The templated microporous compounds [H2(Templ.)][MnII{B2P3O12(OH)}], [templates: 1,3-diaminopropane, C3H10N2 (DAP); piperazine, C4H10N2 (PIP); 1,4-diazacyclo[2.2.2]octane, C6H12N2 (DABCO)] were prepared under mild hydrothermal conditions. The crystal structures (H2DAP-Mn: Pmc2(1) (no. 26), a=1259.43(5), b=949.86(5), c=1135.92(5) pm, Z=4; H2PIP-Mn: Ima2 (no. 46), a=1257.9(1), b=948.69(8), c=1158.19(8) pm, Z=4; H2DABCO-H2PIP-Mn: Ima2 (no. 46), a=1262.90(7), b=961.05(5), c=1151.42(7) pm, Z=4) are characterized by identical framework connectivities [MnII{B2P3O12(OH)}]2-, but vary in shapes (diameters) of the structural channels depending on the shapes of the templating molecule ions. The situation clearly reflects the directing effect of true templates during endotemplating reactions. The experimental results (preparation, chemical analyses, and X-ray refinements) are supported by detailed ab initio calculations (structure optimizations).

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PubMed2006

An atomistic simulation scheme for modeling crystal formation from solution.

We present an atomistic simulation scheme for investigating crystal growth from solution. Molecular-dynamics simulation studies of such processes typically suffer from considerable limitations concerning both system size and simulation times. In our method this time-length scale problem is circumvented by an iterative scheme which combines a Monte Carlo-type approach for the identification of ion adsorption sites and, after each growth step, structural optimization of the ion cluster and the solvent by means of molecular-dynamics simulation runs. An important approximation of our method is based on assuming full structural relaxation of the aggregates between each of the growth steps. This concept only holds for compounds of low solubility. To illustrate our method we studied CaF2 aggregate growth from aqueous solution, which may be taken as prototypes for compounds of very low solubility. The limitations of our simulation scheme are illustrated by the example of NaCl aggregation from aqueous solution, which corresponds to a solute/solvent combination of very high salt solubility.

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