Editing Cell parameters

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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" [http://www.webelements.com/]) 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