From: dakupoto@gmail.com   
      
   Could some physics guru here please help ? I have recently written and tested   
   some C and Python code to compute the energy band structure for common   
   semiconductor materials as Si, Ge, InP(FCC conventional lattice) and GaN(   
   both FCC and HCP conventional lattices) using the empirical pseudopotential   
   method(EPM). The point that I am not very sure about is how to compute the   
   reciprocal lattice k vectors, for both of these   
   conventional lattices. Specifically, given a reciprocal lattice Hamiltonian   
   H = sum(KE_constant*|k + G|^2*del_Kr + FF_SYM(G-G')*cos((G-G').tau) +   
          j FF_ASYM(G-G')*sin((G-G').tau)   
   where KE_constant = hbar^2/2*m_prime ...   
   del_Kr is the Kronecker delta function   
   FF_ASYM, FF_SYM are the asymmetric|symmetric form factors   
   tau is the mid-point interatomic distance   
   Questions are:   
   1. How to compute the k vectors, given the reciprocal lattice's   
   symmetry points   
   2. For the Wurtzite isotope of GaN, what is tau, as there are two   
   conventional lattice interatomic distances - 5.186 A and 3.186 A   
   All hints, suggestions will be gratefully accepted. Thanks in   
   advance.   
      
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