5(a) Use the HF/3-21G or B3LYP/6-31G(d) level of theory to calculate the vibrational frequencies for the following C=O compounds, CH₂O, ClCHO, Cl₂CO and F₂CO.  For each molecule, animate the modes. Provide an explanation for the trend in the C=O stretching frequency.  Compare the results with the experimental values found at webbook.nist.gov.  For each molecule, prepare a table giving the calculated frequencies (scaled with the appropriate scale factor) and experimental frequencies and the description of each mode.  Prepare a plot comparing the calculated frequencies and experimental frequencies. 

5(b) Find a suitable paper describing ab initio or DFT calculations and provide a one page report.