H2O dimer

FA. Diphosphates, etc., without OH and H2O dimers of corner-sharing RO4 tetra-hedra... 

M. P. C. M. Krijn and D. Feil,/ Chem. Phys., 89, 5787 (1988). A Local Density-Functional Study of the Electron Density Distribution in the H2O Dimer. 

Whereas Me2BNH2 is a gas at room temperature (bp 274 K) and reacts rapidly with H2O, dimer 12.32 has a melting point of 282 K and is kinetically stable towards hydrolysis by water. 

For the water-metal interaction, extended tests of the dependency of results on the basis set used were also performed using the CU-H2O dimer as a test case. The full electron description was used for the reference system. The results, calculated using the B3LYP method combined with different basis sets, were compared with those obtained at the standard HF and MP4 levels. Consequently, the least extended LANLIMB basis set was chosen for copper and the tests were focused on the choice of the basis set for the water molecule. Of all tests performed the B3LYP/ MB-6-31G method was found to give the best estimates for the CU-H2O system. An energy of -37.5 kJmol was obtained with this basis set for the ion-copper interaction the reference level defined by the MP4/full electron calculations is —42.3 kJmol. It should be mentioned that both results are close to the experimentally suggested estimate of the interaction of the water molecule with the copper electrode,ca -35 kJmoL. ... 

CI2, Bt2,12 and dihalogen compounds XX react with electron donors like amines or ethers to form complexes where the dihalogen molecules act as electron acceptors. The structure of some such complexes will be discussed in Section 18.6. Similarly the hydrogen halides HX react with electron donors to form hydrogen-bonded complexes, and the structures of some of them will be described in Section 18.7. The chapter ends with descriptions of the structures of the hydrogen-bonded H2O dimer in the gas phase, of solid ice and liquid water, and a brief account of the poly water episode. 

Eckart and Sadlej have calculated the electronic and vibrational contributions to the dipole moment and a and P for the HF and H2O dimers. They find relatively small vibrational contributions to p and a but the vibrational contribution to the first hyperpolarizabihty is predicted to be of the same magnitude as the... 

Intermed. in synth. of labelled aldoses. Prisms (H2O) (hydrate) needles (CeH ) (anhyd.). Mp 182-184°. [a]o -25.9 (H2O). Dimeric in ciyst. state by intermolecular aldol condensation. 

Fig. 4.8 The A X transition energies for the H2O dimer (rfi-H20 a) and rf -H20 (h)), H2O-Li+, H20-Na+, and H2O-K+ complexes calculated by M06-2X/6-3H--FG at various txi-a distances. The longest and shortest ro A distances correspond with the lengths between the inner and outer positions of the hydration shell edges of each cation. The broken line shows the A <— X transition energy of the H2O monomer (From Ref. [43])...

In this subsection, we will address all four types of bound systems traditional, strongly bound molecules (CH, HF, N2, CO, CH , and C2H ) hydrogen-bonded complexes (HF and H2O dimers) weakly bound complexes (ArHF and ArHCl) and very weakly bound complexes (Nc2). The basis set demands, as well as the demands on the electronic structure method, are different for these four classes of molecular systems. We shall discuss each separately, focusing on and Tg as these quantities are critical for characterizing chemical bonds. 

Unit 4 The H2O dimer (stationary points on PES basis set superposition error)... 

All of the differences between the MK and RVS methods tend to zero as the intermolecular separation is increased, and so serious differences are expected to arise only for strongly interacting systems. To demonstrate this point. Table 4 presents a comparison between the MK and RVS analysis for H2O dimer and OC-BH3 calculated at the RHF/6-3H-G(d,p) level of theory.In the relatively weakly interacting water dimer there are small differences between the two methods. Notably, the two methods differ with regard to which water molecule contributes most to the polarization energy. The difference in the two methods is much more pronounced for the OC-BH3 system. For the MK analysis, the dominant term is mix, so this theoretical approach is for all practical purposes invalid. The RVS analysis is much more robust, presumably owing to its inclusion of Pauli repulsion. 

Simple molecular aggregates are amenable to detailed ab initio molecular orbital calculations of vibrational modes, which can be compared to experiment to resolve structural dilemmas. For instance theory predicts that the linear-asymmetric H2O dimer is more stable than the cyclic-symmetric alternative. Consistent with theory, the low-temperature matrix spectrum can only be fitted to the linear structure. 

To test the ReaxFF potential for proton transfer we considered a H2O dimer (Figure 6.10). In this system, we monitored the barrier for... 

---