Convert XDATCAR(VASP) trajectory to unwraped xyz file (**Python**)
===========
Usage:   ./a.out

::

      #lipai@mail.ustc.edu.cn
      #convert XDATCAR to unwraped xyz file
      import numpy as np
      from copy import deepcopy
      
      xdatcar = open('XDATCAR', 'r')
      xyz = open('XDATCAR.xyz', 'w')
      
      system = xdatcar.readline()
      scale = float(xdatcar.readline().rstrip('\n'))
      print(scale)
      
      #get lattice vectors
      a1 = np.array([ float(s)*scale for s in xdatcar.readline().rstrip('\n').split() ])
      a2 = np.array([ float(s)*scale for s in xdatcar.readline().rstrip('\n').split() ])
      a3 = np.array([ float(s)*scale for s in xdatcar.readline().rstrip('\n').split() ])
      
      comment='Lattice=\"'+str(a1[0])+' '+str(a1[1])+' '+str(a1[2])
      comment=comment+str(a2[0])+' '+str(a2[1])+' '+str(a2[2])
      comment=comment+str(a3[0])+' '+str(a3[1])+' '+str(a3[2])+'\"'
      
      #Read xdatcar
      element_names = xdatcar.readline().rstrip('\n').split()
      
      element_dict = {}
      element_numbers = xdatcar.readline().rstrip('\n').split()
      
      Natom = 0
      Ntype = len(element_names)
      Nname=[]
      for t in range(Ntype):
          Natom += int(element_numbers[t])
          for i in range(int(element_numbers[t])):
              Nname.append(element_names[t])
      
      print(Ntype,Natom)
      
      f_prev=np.zeros([Natom,3])
      f_next=np.zeros([Natom,3])
      while True:
          line = xdatcar.readline()
          if len(line) == 0:
              break
          xyz.write(str(Natom) + "\n"+comment+"\n")
      
          for atom in range(Natom):
              p = xdatcar.readline().rstrip('\n').split()
              f_next[atom,:] = np.array([ float(s) for s in p ])
              for x in range(3):
                  if(f_next[atom,x]-f_prev[atom,x]<-0.5):
                      f_next[atom,x]+=1
                  elif(f_next[atom,x]-f_prev[atom,x]>0.5):
                      f_next[atom,x]-=1
      
              c_coords=f_next[atom,0]*a1+f_next[atom,1]*a2+f_next[atom,2]*a3
              xyz.write(Nname[atom]+" "+str(c_coords[0])+" "+str(c_coords[1])+" "+str(c_coords[2])+"\n")
      
          f_prev=deepcopy(f_next)
      
      xdatcar.close()
      xyz.close()