Uploaded by Kasmui Kimia

GAMESS Background

(a computational chemistry website)
Computational Chemistry allows Chemists to analyze properties of molecules using a
computer. The computer can predict quantities such as: molecular geometry (bond length, bond
angle), molecular orbitals, bonding, spectroscopy, and energy. It can also simulate the motion of
molecules (molecular dynamics).
In general, performing a computation involves three steps:
1. Describe your molecule to the computer and tell it what you want it to calculate. If
you wanted to calculate the bond length in carbon dioxide you would specify an initial guess for
the (x,y,z) coordinates of the three atoms. Then you would add some keywords to tell the
computer to find the optimum geometry. On the chemcompute website this is accomplished by
drawing your molecule in the “Submit” tab above.
2. Perform the calculation (“Submit Job”). You run a program on your computer using
the information from step 1 as the input. The computer program will do the calculations and
generate some output for you. On this website the computer program for this calculation is
called “GAMESS” and the computers it will run on are either in my laboratory or on the super
computer “Comet” at the San Diego Supercomputing Center. You must register an account
(click login above) and have me verify your account to access Comet.
3. View the output. You could look at the computer output (it’s a text file). It will tell
you the optimum (x,y,z) coordinates of the atoms in carbon dioxide that it calculated. But it’s
easier to look at the molecule graphically. The “Job Status” tab allows you to do that. You can
view the bond length, bond angle, molecular orbitals, IR vibrations, etc. on this page. You can
also submit another calculation to follow up on your study of the molecule from this page.