GULP output

Let's go through the most important parts of the GULP output file, for the example of one of the vacancy supercell calculations:

Formula = Au255

Check to make sure that you simulated what you wanted to! Examining this line indicates that the input files we created already included a vacancy.

Cartesian lattice vectors (Angstroms) : 16.312068 0.000000 0.000000 0.000000 16.312068 0.000000 0.000000 0.000000 16.312068 Cell parameters (Angstroms/Degrees): a = 16.3121 alpha = 90.0000 b = 16.3121 beta = 90.0000 c = 16.3121 gamma = 90.0000

Crystallographic information. This simple case shows that we have a cubic cell that is 4 fcc Au conventional cells on each side.

-------------------------------------------------------------------------------- No. Atomic x y z Charge Occupancy Label (Frac) (Frac) (Frac) (e) (Frac) -------------------------------------------------------------------------------- 1 Au c 0.000000 0.000000 0.250000 0.0000 1.000000 2 Au c 0.000000 * 0.000000 * 0.500000 * 0.0000 1.000000 3 Au c 0.000000 * 0.000000 * 0.750000 * 0.0000 1.000000 etc...

Fractional coordinates of all the atoms in the simulation.

-------------------------------------------------------------------------------- Atom Types Potential A B C D Cutoffs(Ang) 1 2 Min Max -------------------------------------------------------------------------------- Au c Au c Lennard 12 6 0.214E+06 625. 0.00 0.00 0.000 40.000 --------------------------------------------------------------------------------

The potential parameters we are using, which of course come directly from the input file.

Start of bulk optimisation : Cycle: 0 Energy: -998.396806 Gnorm: 0.033248 CPU: 1.590 ** Hessian calculated ** Cycle: 1 Energy: -998.451903 Gnorm: 0.000832 CPU: 4.020 Cycle: 2 Energy: -998.451930 Gnorm: 0.000025 CPU: 5.810 **** Optimisation achieved ****

If we set "opti" in our input file, GULP will iteratively minimize the energy of the system by relaxing atomic coordinates. Notice how the energy drops after each iteration.

Total lattice energy = -998.45192969 eV

Our final energy: the most important number in the output file!