## Si2 singlet excited state*

 Si1 = Si2
Tell me about the atomic charges, dipole moment, bond lengths, angles, bond orders,
molecular orbital energies, or total energy.
Tell me about the best Lewis structure.

## Atomic Charges and Dipole Moment

SI1 charge=-0.000
SI2 charge= 0.000
with a dipole moment of 0 Debye

## Bond Lengths:

between SI1 and SI2: distance=2.343 ang___

## Bond Orders (Mulliken):

between SI1 and SI2: order=2.437___

## Best Lewis Structure

The Lewis structure that is closest to your structure is determined. The hybridization of the atoms in this idealized Lewis structure is given in the table below.

### Hybridization in the Best Lewis Structure

1. A bonding orbital for Si1-Si2 with 1.9989 electrons
__has 89.98% Si 1 character in a s orbital
__has 10.02% Si 2 character in a p3 hybrid

2. A bonding orbital for Si1-Si2 with 2.0000 electrons
__has 50.00% Si 1 character in a p-pi orbital ( 99.51% p 0.49% d)
__has 50.00% Si 2 character in a p-pi orbital ( 99.51% p 0.49% d)

3. A bonding orbital for Si1-Si2 with 2.0000 electrons
__has 50.00% Si 1 character in a p-pi orbital ( 99.51% p 0.49% d)
__has 50.00% Si 2 character in a p-pi orbital ( 99.51% p 0.49% d)

4. A bonding orbital for Si1-Si2 with 1.9989 electrons
__has 10.02% Si 1 character in a p3 hybrid
__has 89.98% Si 2 character in a s orbital

-With core pairs on:Si 1 Si 1 Si 1 Si 1 Si 1 Si 2 Si 2 Si 2 Si 2 Si 2 -

## Molecular Orbital Energies

The orbital energies are given in eV, where 1 eV=96.49 kJ/mol. Orbitals with very low energy are core 1s orbitals. More antibonding orbitals than you might expect are sometimes listed, because d orbitals are always included for heavy atoms and p orbitals are included for H atoms. Up spins are shown with a ^ and down spins are shown as v.

18 ----- 0.032

17 ----- -2.587

16 ----- -3.040

15 ----- -5.499

14 -^-v- -5.043
13 -^-v- -5.122

12 -^-v- -9.164

11 -^-v- -12.72

10 -^-v- -94.83
9 -^-v- -94.84

8 -^-v- -95.02 7 -^-v- -95.02

6 -^-v- -95.39 5 -^-v- -95.39

4 -^-v- -137.4 3 -^-v- -137.4

2 -^-v- -1773. 1 -^-v- -1773.

## Total Electronic Energy

The total electronic energy is a very large number, so by convention the units are given in atomic units, that is Hartrees (H). One Hartree is 2625.5 kJ/mol. The energy reference is for totally dissociated atoms. In other words, the reference state is a gas consisting of nuclei and electrons all at infinite distance from each other. The electronic energy includes all electric interactions and the kinetic energy of the electrons. This energy does not include translation, rotation, or vibration of the the molecule.

Total electronic energy = -578.8783769613 Hartrees

*K. P. Huber and G. Herzberg, p 592, indicate the ground state is a triplet state with the same orbital ordering as O2 (3Sigma -g is lower in energy than the 3Pi u ). Therefore, this singlet state is not the ground state. Very careful ab initio calculations suggest this state is also not the first excited state. See C. W. Bauschlicher, S. R. Langhoff, J. Chem. Phys.,1987, 87, 2919-24, and M. R. Nimbus, L. B. Harding, G. B. Ellison, J. Chem. Phys., 1987, 87, 5116. Please also check the lower energy triplet state calculation.