LAMMPS Assignment
Overview
This assignment was largely unable to be completed. Progress was made towards the objective of calculating the interatomic potentials as well as the calibration of MEAM potential using response surface.
Interatomic Potentials
The process for generating the interatomic potentials began with several potential inputs. The cohesive energy, 3.39 ev/atom, was set first. The parameters α and re were then calculated from the two equations below. The other parameters where chosen randomly.
Once calculated, these parameters were input into the library.meam file seen below.
#MEAM data # elt lat z ielement atwt # alpha b0 b1 b2 b3 alat esub asub # t0 t1 t2 t3 rozero ibar 'Al' 'fcc' 12 13 26.981500 5.017950 10.030000 5.030000 8.130000 10.930000 4.050000 3.430000 3.878000 1.948000e+01 18.080000 91.980000 23.280000 1 0
Once the MEAM files were written the MatPro.py program, provided at [1], was run to calculate cohesive energy, lattice constant, bulk modulus, equilibrium volume, elastic constants c11, c12, and c44, surface formation energies for (100), (110), and (111), and defect energies vacancy and self-interstitial formation for the fcc structure. Once run the bounds set for each MEAM potential parameter had to be evaluated. This was done using a matlab script provided at [2]. This resulted in several output files. The first was Al_coarse_pot_eval_data.mat, provided below, and several text files which are also shown below.
Calibration of MEAM potential using response surface
The sensitive parameters determined previously would be used to solve for the MEAM potential. Since the sensitive parameters were unable to be determined the potential was never calculated. A test run was performed which varied all twelve parameters. To reduce the time requirements N had to be significantly reduced, affecting the accuracy for many of the parameters. The results of this run are shown below.
