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QMD-MGDFT/init_pos.c

QMD-MGDFT/init_pos.c

NAME

   Ab initio real space code with multigrid acceleration
   Quantum molecular dynamics package.
   Version: 2.1.5

   Copyright (C) 1995  Emil Briggs
   Copyright (C) 1998  Emil Briggs, Charles Brabec, Mark Wensell, 
                       Dan Sullivan, Chris Rapcewicz, Jerzy Bernholc
   Copyright (C) 2001  Emil Briggs, Wenchang Lu,
                       Marco Buongiorno Nardelli,Charles Brabec, 
                       Mark Wensell,Dan Sullivan, Chris Rapcewicz,
                       Jerzy Bernholc

FUNCTION

   void init_pos()
   if positions are read in cartesian coordinates, get crystal coordinates
   if positions are read in crystal coordinates, get cartesian coordinates

INPUTS

   nothing

OUTPUT

   coordinates are stored in ct.ion

PARENTS

   init.c

CHILDREN

   to_cartesian.c

SOURCE

      
    #include <float.h>
    #include <math.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include "md.h"
    #include "recips.h"
    
    #define     SR2         1.414213562373
    #define     SR3         1.732050807569      
    
    void init_pos()
    {
        int i, ir;
        ION *iptr;
    
        /* Scale the ion-coordinates by the lattice vectors (if required) */
        
        if(ct.crd_flag){
          
          /* If the positions are in crystal coordinates
             get cartesian coordinates */
          
          /* add part to bring into supercell (just in case) */
          
          for(i = 0;i < ct.num_ions; i++){
    
            iptr = &ct.ions[i];
    
            for(ir = 0; ir < 3; ir++){
              iptr->xtal[ir] = iptr->crds[0]*b0[ir] 
                + iptr->crds[1]*b1[ir] +  iptr->crds[2]*b2[ir];
            } /* end for ir */   
    
            if(ct.ibrav == HEXAGONAL){
    
              iptr->xtal[0] = (iptr->crds[0] - iptr->crds[1]/SR3) / ct.celldm[0];
              iptr->xtal[1] = iptr->crds[1]/(SR3/2.0) / ct.celldm[0];
              iptr->xtal[2] = iptr->crds[2]*b2[2];
    
              if(iptr->xtal[0] < 0.0)iptr->xtal[0]+=1.0;
              if(iptr->xtal[1] < 0.0)iptr->xtal[1]+=1.0;
              if(iptr->xtal[2] < 0.0)iptr->xtal[2]+=1.0;
              if(iptr->xtal[0] > 1.0)iptr->xtal[0]-=1.0;
              if(iptr->xtal[1] > 1.0)iptr->xtal[1]-=1.0;
              if(iptr->xtal[2] > 1.0)iptr->xtal[2]-=1.0;
    
            } /* end if */
            to_cartesian(iptr->xtal, iptr->crds);
    
          } /* end for i */
        }else{
          /* if positions in cartesian coordinates
             get crystal coordinates */
          
          /* add part to bring into supercell (just in case) */
          for(i = 0;i < ct.num_ions; i++){
            iptr = &ct.ions[i];
            for(ir = 0; ir < 3; ir++){
              iptr->crds[ir] = iptr->xtal[0]*ct.a0[ir] 
                + iptr->xtal[1]*ct.a1[ir] 
                + iptr->xtal[2]*ct.a2[ir];
            } /* end for ir */
    
          } /* end for i */
        } /* if(ct.crd_flag) */
        
    } /* end init_pos */

TABLE OF CONTENTS

QMD-MGDFT/init_pos.c