Using pseudo-potentials and larger basis sets

Important You can carry out this calculation on your lap-top.

Create a Molecule of TlCl₃

• First, if you have any other "molecule" windows open, close them
• Then choose file -> new -> create mol group. A new blank molecule window should appear

  

• on the controls palette click on the button that has a grey periodic table (or element fragment) on it:

  

• when the periodic table comes up choose Tl for Thallium (1.), then when the thallium options appear along the bottom of this window choose the planar fragment (2.):

  

• now move the mouse to the molecule window and click once inside this window, a molecule of TlH₃ will appear
• now go back to the periodic table and choose Cl for chlorine (1.), then when the bonding options appear along the bottom of this window choose the atomic fragment (2.):

  

• now move the mouse to the molecule window and click ontop of the H atoms, they will turn into Cl atoms. It is worth noting that this "trick" will work with functional groups as well as atoms.

  

• on the controls pallette click on the button with a question-mark in front of a ruler. This is the inquiry button and we will use it later, however once in inquiry mode the other buttons deactivate and this will stop you accidentially making changes to your molecule.

Set up the calculation for TlCl₃

• From the main menu along the top of the screen (in gaussview) choose "Calculation" and then choose "Gaussian":

  

• a new palette will appear the calculation palette. It opens with the "job type" tab open. Use the pull down menu under "energy" to choose "optimization" (ignore the other stuff that appears)
• then click on the "method" tab to open it, use the pull down menu under "Hartree-Fock" to pick "DFT", some of the entries will change, find the pull-down menu "LSDA" and choose "B3LYP" (don't change anything else!)
• then click on the "title" tab to open it, and type "TlCl3 optimisation"
• then just below this where is says "basis set" use the pull-down menue to choose the LanL2MB options (1.), this uses a medium level basis set: D95V on first row atoms and Los Alamos ECP (ie pseudo potentials) on heavier elements. You only need to know that these are "medium" level you don't need to remember the names, the reason we don't use better basis sets and pseudo potentials is that the best ones are a bit more technical to implement and will make the calculations take much longer!

  

• then click on the "link 0" tab to open it, and after "%chk=" type "yourname_tlcl3_opt", make sure you type the underscores as the program is sensitive to extra spaces, replace "yourname" with your first name ... remember NO extra spaces!! For example you might have "sally_tlcl3_opt"
• check that the red boxed lines (2.) are similar to that in the image above.
• Then press submit (button is in the bottom left of the palette):
• a new window will then pop-up and ask you for a file name, navigate to the folder you created at the begining and then use exactly the same name as you put in the "%chk=" part, ie "yourname_tlcl3_opt", then press "save":
• a new window will then pop-up and ask you if you want to submit the job, press submit!
• close the molecule window, this is important as the "finished" molecule will look very similar to your starting one and many students accidentally take the wrong molecule!
• wait for the message "Gaussian Job Completed ...", and click yes for opening a results file.
• a new window will open, make sure that the file type is for "Gaussian Output Files (*.out *.log) and select your .out or .log file, and then click open. A new molecule window should apear with your optimized molecule in it. Important Deposit your completed population analysis in the chemical database "D-space", and link to this on your wiki, you will loose marks if this file is not part of your wiki.

Find information about TlCl₃ similarly to our previous calculations

• on the comands palette click on the button with a question-mark in front of a ruler. This is the inquiry button and will tell you bond distances if you click on two atoms, and bond angles if you click on three atoms
• include in your wiki
  • What is the optimised Tl-Cl bond distance?
  • What is the optimised Cl-Tl-Cl bond angle?
• click on the results tab at the top and choose "Summary". This will open a window that lists important information about your calculation.
  • What is the file type?
  • What is the calculation type?
  • What is the calculation method?
  • What is the basis set?
  • What is the final energy in atomic units (au)?
  • What is the dipole moment?
  • What is the point group of your molecule?
  • How long did your calculation take?
• When you are ready close the molecule window move onto the next step.