The Hydrogen Fluoride Dimer HF

As a typical quantitative example of formation of a H-bonded structure as a consequence of the electrostatic interactions between the individual molecules, we choose the (HF)2 homodimer. To give the best description 

4 cos0a(3—5cos20b)cos0b + 3 sin0 sin0B (5cos20b—l)cos ) 

Point-like linear multipoles are assumed to be placed in the centre of mass of the molecule. 

4 cos0a(3—5cos 0a)cos0b + 3 sin0A(5cos 0A—l)sin0B cos ) 

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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. 

The HF-HF hydrogen fluoride dimer, composed of a modest four nuclei and twenty electrons, represents the simplest example of a hydrogen... 

Michael, D. W., Dykstra, C. E., and Lisy, J. M., Changes in the electronic structure and vibrational potential of hydrogen fluoride upon dimerization A well-correlated (HF) potential energy surface, J. Chem. Phys. 81, 5998-6006 (1984). 

D. W. Michael, C. E. Dykstra, and J. M. Lisy, ]. Chem. Phys., 81,5998 (1984). Changes in the Electronic Structure and Vibrational Potential of Hydrogen Fluoride Upon Dimerization A Well-Correlated (HF)2 Potential Energy Surface. 

Hydrogen fluoride vapors contain monomeric HF molecules, dimers (HF)2 and polymeric species, (HF) , with n varying from 3 to 8. The stmctures of the polymers remain unknown, but the stmcmre of the dimer has been determined by spectroscopic measurements and by high-level quantum chemical calculations. The structure indicated in Fig. 18.8 represents a recommended structure based on information from both experiments and calculations [12]. The complex consists of two monomeric units with essentially the same H-F bond distance as in an isolated monomer. The monomers are joined through a H- F bond which is twice as long as bond distance in the monomer, but nearly 100 pm shorter than the sum of the van der Waals radii of H and F (Table 8.4). Note the similarity to the structure of HFICI (Fig. 18.6). The dissociation energy of the dimer at zero kelvin is Do = 13 kJ mol [13]. 

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