Hydrogen Chloride

Below shows the calculated structure of HCl from DZV calculations. It's a simple linear molecule with a bond length of 0.138 nm. This normally being .127 nm long from experimental results.

HCl's highest occupied molecular orbital in its ground state is shown below.
This showing the filled 3p non bonding orbital

HCl's lowest unoccupied molecular orbital which would be filled first when excited is shown below.
This showing the empty 3p anti-bonding orbital

The electrostatic potential and partial atomic charges are shown below.
The chloride being large and more electronegative than the hydrogen has a large negative potential around it, which the small hydrogen has a small positive potential.

For more visual representations, the HCl Molecular Orbital Diagrams can be viewed.

HCl Vibrational Energies were also calculated.


Dipole Moments

This molecule was run through multiple steps molecular orbital calculations, these data sets were first compared at these different levels of theory by measuring dipole moments.

Physical measurements = 1.05 debyes
AM1   = 1.3840 debyes
6-21G = 1.9047 debyes
6-31G = 1.9028 debyes
DZV   = 1.9158 debyes

For these calculations, the first level of MO calculations AM1 gives he closest to reference results, the next three levels all giving near the same reading =/- 0.011

Improving Dipole Moments

These calculations were further improved by diffusing the elections on the S shell by changing the number of D Heavy, F Heavy, and Light Polarization functions respectively.

Physical measurements = 1.05 debyes

AM1 does not allow for this change in diffusing.

6-21G (1,0,1) = 1.4903 debyes

6-21G (3,0,3) = 1.1765 debyes

6-31G (1,1,1) = 1.4852 debyes
6-31G (3,1,3) = 1.1701 debyes

DZV   (1,1,1) = 1.4835 debyes
DZV   (1,1,2) = 1.3785 debyes
DZV   (2,1,2) = 1.2586 debyes
DZV   (3,1,3) = 1.1534 debyes

The higher the number of polarization functions, the lower the calculated energy. This is done from the polarization allowing the molecule to allow it's electrons to move around more freely. From this, the furthest level of calculations with the highest amount of polarization functions gives the closest to reference results for dipole moment.


Potential Energy surface versus Bond length was also calculated.



This energy being lowest at 0 nm for all levels of calculation theory.  6-31G calculations giving the lowest energy of the three. this energy is quickly rising when bond lengths are below 0, and quickly rising but plateauing when going above 0.