Cell parameters

by Jaime version VASP4.6

Calculations have been performed for Ag, Au, Cu, Ir, Ni, Pd, Pt and Rh in faced-centered cubic (fcc) structure, the most stable for all of them. Metal bulk have been calculated performing a Brillouin-zone integration with grids of 11x11x11 Monkhorst-Pack k-points. The core electrons are described by the Projector Augmented Wave method pseudopotentials (PAW) supplied by VASP, with a cutoff of 400 eV. For the exchange and correlation functional the Revised Perdew-Burke-Ernzerhof (RPBE) was used. In order to optimize the cell parameter a, a scan around the expected value (for example the experimental one) is performed. That is, we select a set of values close to the experimental one, and calculate the energy for each one. Then we fit a third degree polynomial function with the energy versus the selected values as variables, and locate the minimum. This is the selected value.

Table shows the calculated (Calc.) and experimental (Exp. extracted from "web elements" [1]) values in ångströms (Å), and the error between them in percentage.

                       Calc.    Exp.   Error
                                                    
             Ag       4.227   4.0853     3    
             Au       4.208   4.0782     3      
             Cu       3.676   3.6149     2     
             Ir       3.879   3.839      1  
             Ni       3.551   3.524      1   
             Pd       3.987   3.8907     2    
             Pt       3.990   3.9242     2      
             Rh       3.856   3.8034     1