Theoretical predictions of properties and volatility of chlorides and oxychlorides of group-4 elements. II. Adsorption of tetrachlorides and oxydichlorides of Zr, Hf, and Rf on neutral and modified surfaces

Pershina, V., Borschevsky, A., Ilias, M. & Tuerler, A., 14-Aug-2014, In : Journal of Chemical Physics. 141, 6, 7 p., 064315.

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With the aim to interpret results of gas-phase chromatography experiments on volatility of group-4 tetrachlorides and oxychlorides including those of Rf, adsorption enthalpies of these species on neutral, and modified quartz surfaces were estimated on the basis of relativistic, two-component Density Functional Theory calculations of MC14, MOC12, MCl6-, and MOCl42 with the use of adsorption models. Several mechanisms of adsorption were considered. In the case of physisorption of MCl4, the trend in the adsorption energy in the group should be Zr > Hf > Rf, so that the volatility should change in the opposite direction. The latter trend complies with the one in the sublimation enthalpies, Delta H-sub, of the Zr and Hf tetrachlorides, i.e., Zr <Hf. On the basis of a correlation between these quantities, Delta H-sub(RfCl(4)) was predicted as 104.2 kJ/mol. The energy of physisorption of MOC12 on quartz should increase in the group, Zr <Hf <Rf, as defined by increasing dipole moments of these molecules along the series. In the case of adsorption of MCl4 on quartz by chemical forces, formation of the MOCl2 or MOCl42- complexes on the surface can take place, so that the sequence in the adsorption energy should be Zr > Hf > Rf, as defined by the complex formation energies. In the case of adsorption of MCl4 on a chlorinated quartz surface, formation of the MCl62- surface complexes can occur, so that the trend in the adsorption strength should be Zr <Hf <Rf. All the predicted sequences, showing a smooth change of the adsorption energy in the group, are in disagreement with the reversed trend Zr Rf <Hf, observed in the "one-atom-at-a-time" gas-phase chromatography experiments. Thus, currently no theoretical explanation can be found for the experimental observations. (C) 2014 AIP Publishing LLC.

Original languageEnglish
Article number064315
Number of pages7
JournalJournal of Chemical Physics
Issue number6
Publication statusPublished - 14-Aug-2014
Externally publishedYes



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