User`s guide

7. Exercises
despite the short distance between the H atoms.] Close the Advanced Job Options window.
Check Preview Input File and submit the job.
Describe the general appearance of the input file. Specifically, how does it differ from other input
files? Submit the job.
Provide a picture of the transition state for this reaction. Which H atoms are forming molecular
hydrogen? What is their bond length, and how does that compare to the atom distance between
the two H atoms in SiH
2
? in H
2
? How does their bond angle with Si compare to the SiH
2
bond
angle?
Describe how the transition state search algorithm for a saddle calculation differs from a
Transition State Optimization. When would you use each algorithm?
E. Frequency Calculations
14. Normal Vibrational Modes of Formaldehyde
Build formaldehyde, H
2
CO, and perform a Geometry Optimization PM3 calculation on it. View
the result, click on New Job Using This Geometry, and perform a Vibrational Frequencies PM3
calculation. View the result, and view each vibrational mode. Fill in the following table of
vibrational frequencies by visually identifying the description of each normal mode.
Mode Description
PM3
Frequency
(cm
−1
)
Literature
Frequency
(cm
−1
)
ν
1
sym CH stretch 2811
ν
2
CO stretch 1756
ν
3
CH
2
bend 1500
ν
4
out-of-plane bend 1170
ν
5
antisym CH stretch 2861
ν
6
CH
2
rock 1251
15. Stationary Points of Vinyl Amine
Build planar and pyramidal vinyl amine, CH
2
=CHNH
2
.
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