Chem3D software Task

UOIT/Science

CHEM 2010u

Structure and Bonding

Project 2

Issue date: Nov 13, 2019

Return date: Nov 25, 2019 or earlier

(via Blackboard as attachment to message)

Student 1 last name, first name
Student 1 ID card №

Instructions: Prepare the assignment as a word file with your answers type-written.

Keep the title page and description (next page).

Copy work from relevant software (if used) to this file, with pictures

cropped (no full screens).

Late returns are not accepted.

In case of identical works from different students, the mark is divided by the number of copies.

1. Consider the OH molecule.

Use Chem3D (see Reference in problem sets, use Restricted for open shell, if needed) to obtain its energy curve E(R) as described here:

(a) Calculate total energies (in kcal/mol – from Chem3D) separately for each of O and H

atoms in their ground states (hereafter pay attention to proper spin multiplicities s.m.).

Calculate Eat = sum of these atomic energies.

(b) In the new blue window produce OH and calculate its total energy E for the initial

default equilibrium O-H distance Re in the ground state (in kcal/mol) - via the

following modified sequence (with no Minimize):

Calculations - GAMESS Interface - Compute Properties - (mark) Total Energy,

in same menu click Job & Theory at top-left and from there continue as usual.

(c) At left from the blue window in a table see the coordinates of atoms and edit them to

decrease the O-H distance R by 0.25 Å. Calculate E for this distance – as in (b).

Repeat for R shorter than Re by 0.5 Å.

Now repeat for R = Re + 0.25 Å, Re + 0.5 Å, and then in increments of 0.5 Å, up to 3

Å, checking if E is lower than Eat. Once it is higher, stop.

(d) Compare the numbers of unpaired electrons in OH and in isolated O and H (together).

If they are different, check if s.m. could have changed to that for separated O + H:

calculate E with new s.m. at same R (where E exceeded Eat) and check if now E < Eat.

If yes, continue with the new s.m., increasing R in increments of 0.5 Å, up to 3 Å.

(e) Collect in a table the calculated E values for all R values.

Plot them in a graph with Eat as origin of energy (i.e. plot (E - Eat) values), with

different symbols indicating points for the initial s.m. (of OH) and those for the final

s.m. (of O + H), e.g. in different colour.

Connect the points for each R to get the approximate energy curve E(R).

(f) Evaluate De value and compare it with experimental 430 kJ/mol (bring it to kcal/mol).