NH3-HCI complex

BSSE-Free MCSCF Method for Strong Hydrogen Bonds Investigation of H2O-HCI and NH3-HCI Complexes... 

The NH3-HCI complex represents a useful model system for proton transfer reaction studies, which are of great relevance in chemical and biological phenomena. For this... 

All the data reported in the literature seem to confirm that the NH3-HCI complex possesses C3V symmetry (see Figure 2). Table 4 shows the geometrical parameters of the complex reported in the pertinent literature. Bacskay et al [26,27] confirm the C3V symmetry of the complex both at the MP2 and SCF level. A moderate variation from the C3V symmetry, however, results from EFG (Electric Field Gradient) calculations [22]. 

Table 6 Previously estimated red shift values for the intramolecular stretching frequency of the HCl bond in the NH3-HCI complex...

Comparable results are obtained for the NH3-HCI complex. SCF geometrical parameters (rnci and rnci) vary considerably with the basis set employed, while the MCSCF-Ml and SCF-Ml results are more stable (see Table 9). 

Table 10 SCF, SCF-MI and MCSCF-MI calculated binding energies relative to the equilibrium geometries (reported in Table 7)for the NH3-HCI complex. All the values are in kcal/mol...

Analogous results are obtained for this system, see Table 12. Also in this case the SCF-MI and MCSCF-MI results show a greater stability for what concerns the basis set if compared with the SCF method. The difference between the force constants relative to asymptotic and equilibrium geometries (AK) is positive. The AK for the NH3-HCI complex is greater than that of the H2O-HCI complex. 

BSSE-free MCSCF method for strong hydrogen bonds investigation of H20-HCi and NH3-HCI complexes... 

Table 4 Previously reported geometrical parameters for the NH3-HCI complex. Distances are reported in A and angles in degrees...

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