April 1, 2004
      
                  
        
  Author(s)
  Eric J. Cockayne,   Benjamin P. Burton
 
       
            
    
    
        The polarization of a nearest-neighbor (nn) Pb-O vacancy pair in PbTiO3 is calculated, using the modern theory of polarization, implemented in the density functional theory ultrasoft pseudopotential formalism. The dipole moment per divacancy is about 2.228