1. Mp2 vs. Hartee-Fock
The energy for MP2= -2.8728 Hartrees
The energy for HF= -2.8599 Hartrees
The difference is 0.01291 Hartrees, a difference of 0.45%
There is not much difference in the values for each theory, but MP2 would be
more accurate because it is closer to the experimental value. These values are
approximately the same because the starting points for MP calculations are the
summation of the HF value and the additional excitations.
2. The second order perturbation theory recalculates the function until the psi does
not change anymore. The second order theory is a different theory than the MP2
theory, therefore will result in different methods of calculation for the same order
perturbation. The MP is using the H_0 for an approximation, but in HF, H_0 is
not an approximation, and is assumed completely solvable. Therefore the energy
calculations would become more accurate.
3. MP3= -2.8755
MP4= -2.87617
MP4 is more accurate for the MP calculations because MP4 accounts for more
excitation states of He than MP3 does.
4. CCSD/CCSD(T)=-2.8599
They are both the same value for He because there are no possible combinations
for there to be a triple electron excitation. This means that there would be no
additional terms added to the CCSD(T) calculation and would not be affected by
it.
5. G3, G3(MP2), CCSD(T), CCSD, MP4, MP3, MP2, and HF
6. The ground state of B_2 is ___________________ because _____________
It is important to put the correct multiplicity because it will change the energy of
the calculation.
7. DRAW SCALE WITH DEGENERACY (HOMO/LUMO)
8. The HOMO and LUMO levels do line up with the given number of electrons in
MO. 5 and 6 are the highest occupied and 7 is the LUMO.
9. SHOWN on #7
10. On Handout
11. Shown on #7
12. The HOMO-4 and HOMO-5 states are significantly lower in energy because the
atomic orbitals that form the MO are lower in energy. The MO are 1(sigma)
orbitals, therefore they have lower energy than the remaining electrons and
orbitals.
13. C_2 singlet: -75.3936844
C_2 triplet: -75.488
The triplet is lower in energy and the lower the energy, the better the calculation
because we are using variational method. The triplet is not the representation of
the ground state of the C_2 molecule. The calculations are consistent with the
HD MO Handout. The MP2 energy is -75.719 eV
14. The MP2 energy for triplet is -75.709 eV. The multiplicity of the ground state is
singlet because it has the lower energy.
15. C_2 singlet: -75.716 eV
C_2 triplet: -75.73 eV
For CCSD: The triplet has a lower energy therefore would be lower than the
singlet energy and is ground state.
16. C_2 singlet: -75.747 eV
C_2 triplet: -75.742 eV
For CCSD(T): Singlet is the lowest energy, therefore the ground state.