Which method?
• We’re using Density Functional Theory (DFT) as it gives us the
most accurate results for transition metals in the least amount of
time. We’re using the B3LYP flavor of DFT as it is the most
common one.
Which basis set? Basis sets are approximations of atomic orbitals
• We will be using LANL2DZ for our calculation as it models the
bonding in transition metal complexes well.
What job type?
• Geometry Optimize + Vibrational Frequencies (for reactants or
products)
We are calculating points on the Potential Energy Surface (PES):
Energy and other properties are a function of geometry
Saddle Point
Local maxima
Maxima and Minima are stationary points (1st derivative of PES
=0)
• Minima gives equilibrium structure(s) of reactant or product;
must have NO imaginary frequencies
• Saddle point corresponds to transition structure; transition
states should have ONE imaginary frequency
Input
Initial
Guess
Gaussian
calculates
Integrals
Stationary
Point
reached?
NO
New
Geometry
Guess
YES
You’re
Done!
Geometry Optimized? Should see something like:
Item
Value
Threshold
Converged?
Maximum Force
0.000005
0.000450
RMS Force
0.000002
0.000300
Maximum Displacement
0.000012
0.001800
RMS Displacement
0.000006
0.001200
Predicted change in Energy=-1.586489D-10
Optimization completed.
-- Stationary point found.
YES
YES
YES
YES
Is it a minima? Search for NImag (Should be 0 for minima)
\NImag=0\
Want thermochem data? Search raw output for Kcal
Zero-point vibrational energy
53572.7 (Joules/Mol)
12.80419 (Kcal/Mol)
…
Thermal correction to Gibbs Free Energy=
-0.006541
Sum of electronic and zero-point Energies=
-997.086339
Sum of electronic and thermal Energies=
-997.080515
Sum of electronic and thermal Enthalpies=
-997.079571
Sum of electronic and thermal Free Energies=
-997.113285
Anything else? Click on the magnifying
class to the right of your job in WebMO
Bohr: Atomic unit of Length (a0)
o Equal to the radius of the first Bohr orbit for a hydrogen
atom
o 5.29 x 10-11 m (0.0529 nm, 52.9 pm, 0.529 Å)
Hartree: Atomic unit of Energy
o Equal to twice the energy of a ground state hydrogen
atom
 627.51 kcal/mole
 2625.5 kJ/mole
 27.211 eV
 219474.6 cm-1