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1

On Chemical Bonding Between Helium and Oxygen

Grochala W.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 1

87-122

EN

A brief analysis of the He-O chemical bond, present in cationic (HeO+ź) and a few hypothetical anionic species (XHeO-, X = F, Cl), is performed at various levels of theory. We are also able to propose two candidates for the first metastable neutral molecule which contains helium chemically bound to oxygen: (HeO)(CsF) and (HeO)(NMe4F).

2

Stabilization ofWVI in Nitride Environment via Acid/Base Reactions, and General Route to Layered Transition Metal Nitrides

Grochala W.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 5-6

613-620

EN

DFT calculations for two hypothetical ternary nitrides of hexavalent tungsten: LaWN3 and La2WN4 (in perovskite and K2NiF4 structures, respectively) show that these compounds should spontaneously form fromWN2 (acid) and LaN (base) reagents, or simply from (WN + 1/2 N2 orW+ N2) and LaN, at ambient or elevated temperature and high N2 pressure to speed up the reactions. This concept may be utilized to stabilize other efemeric nitrides, like these of ReVII, OsVIII, and possibly even of unprecedented IrIX. La2WN4 is example of rare two-dimensional nitride materials. Band structure calculations confirm that LaWN3, La2WN4 and several related compounds should exhibitmetallic conductivity, and they show good prospect for 2Dsuperconductivity via self-doping.

3

Thermal Decomposition of Chemical Hydrides

Grochala W.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 6

1087-1092

4

Chemistry of Vibronic Coupling, Part 4: Off-Diagonal Vibronic Coupling Constants Across the Periodic Table

Grochala W., Hoffmann R.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 11

1603-1659

EN

Vibronic coupling for inter–valence charge–transfer states in linear symmetric ABA molecules (A, B = s–, p– or d–block element) is investigated computationally. In particular we examine vibronic coupling as a function of the s, p, d – block nature of the A and B constituent elements. Based on density-functional theory computations for 395 triatomic molecules, we construct a map of a vibronic stability parameter G (defined as the ratio of asymmetric to symmetric stretching force constants) across the periodic table. Correlations of G versus the sum and difference of electronegativities of A and B elements are tested, and also vs. a useful parameter f, the ratio of the sum of electronegativities to an AB separation. Usually, the larger the sum of electronegativities, and the shorter the AB bond, the larger the vibronic instability. The largest vibronic instability thus occurs for interhalogen compounds. Molecules containing d-block elements exhibit trends similar to those of molecules built of p-block elements with similar electronegativities, although the latter are usually more unstable. A molecular orbital model is developed to explain the trends obtained in our computations, as well as to build a framework for systematic manipulation of vibronic coupling constants in molecular systems. From the model we argue that vibronic coupling is usually strongest in systems built of hard Lewis acids and bases.We also show that s–p mixing and “ionic/covalent curve crossing” increase the vibronic instability of a molecule. To attain high vibronic instability, one should build a molecule of light, highly electronegative p–block elements. These findings may be of use in the experimental search for new superconducting materials.