The Hydrogen Fluoride Dimer

Intramolecular force constants Intermolecular force constants 

Both intramolecular force constants are lowered somewhat through complex formation (Table 6). As expected this effect is larger in the proton-donor than in the proton-acceptor molecule. In Table 7 we present calculated and experimental data on the vibrational spectrum of (HF)2. General agreement is obtained. The most remarkable feature is the strict separation of intra- and intermolecular modes on the frequency axis. Hydrogen bond formation is a weak interaction compared to the formation of a chemical bond hence, the normal frequencies are well separated. However, Hartree-Fock calculations of bond stretching force constants 

There are some basic features of hydrogen-bonded complexes which are related to the wave functions and not to the energy surface of the complex. As an example we discuss in section 3.2 the increase in polarity on complex formation in the case of (H20)2 and the experimentally well studied heterodimer H20 HF. 

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Dyke T R, Howard B J and Kiemperer W 1972 Radiofrequenoy and miorowave speotrum of the hydrogen fluoride dimer a nonrigid moieouie J. Chem. Phys. 56 2442-54... 

Systems The Hydrogen Fluoride Dimer , J. Chem. Phys., 101, 9793. 

Latajka, Z., Bouteiller, Y., 1994, Application of Density Functional Methods for the Study of Hydrogen-Bonded Systems The Hydrogen Fluoride Dimer , J. Chem. Phys., 101, 9793. 

Hydrogen fluoride dimer, like with the water dimer, is one of the most frequently studied complexes. Both extensive theoretical and experimental data are available for analysis. The PES of the hydrogen fluoride dimer (see Figs. 15 and 16), if compared with that of water, is simpler two stationary points exist the quasi-linear" structure (see Fig. 15) and the cyclic structure (see Fig. 16). 

Fig. 15. The quasi-linear structure of the hydrogen fluoride dimer.

Concerning ab initio calculations on neutral hydrogen-bonded complexes we consider the simplest example, the hydrogen fluoride dimer (Table 3). Both the equilibrium geometry and energy of interaction strongly depend on the quality of the basis set... 

Cammi, R, Del Valle, F. J. O., and Tomasi, J., Decomposition of the interaction energy with counterpoise corrections to the basis set superposition error for dimers in solution. Method and application to the hydrogen fluoride dimer, Chem. Rhys. 122, 63-74 (1988). 

Hobza, R, Sponer, J., and Polasek, M., H-honded and stacked DNA base pairs cytosine dimer. An ab initio second-order M0ller-Plesset study, J. Am. Chem. Soc. 117, 792-798 (1995). McDowell, S. A. C. and Buckingham, A. D., Isotope effects on the stability of the carbon monoxide-acetylene van der Waals molecule and the hydrogen fluoride dimer, Chem. Phys. Lett. 182, 551-555 (1991). 

Howard, B.J., Dyke, T.R., and Klemperer, W. (1984) The molecular beam spectrum and the structure of the hydrogen fluoride dimer. J. Chem. Phys., 81, 5417-5425. 

Our next example will be the hydrogen fluoride dimer. It is a good example to show that the electrostatics restricted to the dipole-dipole interaction (or the equivalent charge interaction model) is not sufficient to determine the minimum orientation even for interactions of diatomic monomers. Such a model predicts the linear F-H- -F-H structure dictated by the optimal orientation of the dipoles, which disagrees with the observed structure in which the hydrogen acceptor is tilted away from the linear geometry by about 60°... 

C.E. Dykstra, S.-Y. Liu, D.J. Malik, The hydrogen bonding influence on polarizability and hyperpolarizability. A derivative hartree-fock study of the electrical proptaties of hydrogen fluoride and the hydrogen fluoride dimer. J. Mol. StracL THEOCHEM 135(1), 357-368... 

Dyke TR, Howard BJ, Klemperer W. Radiofrequency and microwave spectrum of the hydrogen fluoride dimer a nonrigid molecule. J Chem Phys 56 2442... 

Having defined the BSSE, its origins, and approximate magnitudes, and having discussed how to determine it and reduce it, we move on to several case studies in which BSSE has been the focus of study or deemed to be important in determining the results. We have selected two well-studied systems, the water dimer (H20)2 and the hydrogen fluoride dimer (HFlj, to illustrate the phenomena discussed above and to illustrate how the size of the basis sets, and the number and quality of polarization functions, affect properties such as dipole mo-... 

The hydrogen fluoride dimer and the water dimer are small in size and thus large basis sets approaching saturation have been used to study their properties. 

T. R. Dyke, B. J. Howard, and W. Klemperer, J. Chem. Phys., 56, 2442 (1972). Radiofrequency and Microwave Spectrum of the Hydrogen Fluoride Dimer A Nonrigid Molecule. 

Geometry of the hydrogen fluoride dimers. The axis is inclined to the F-F axis by 1.3-pending upon the isotropic species. 2.5° de-... 

The pair interaction potential of the hydrogen fluoride dimer represents an ideal case study for experimental and theoretical research in the field of weak intermolecular interactions and hydrogen-bonding, aiming at an improved understanding of HF vapor. 

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