x Phi(i1,i2, na, nb) for pairs of atoms in the super-cell with the relative= positions given by R =3D (i-1)*a + (j-1)*b +(k-1)*c where i j and k are read from Al444.fc file. However, such a supercell does not include the pair of atoms located along= the cube axis direction i.e R =3D (a,0,0) or (0,a,0) or (0,0,a), and hence= the calculation CAN NOT give us the force-constant matrices along those pa= ir of atoms. How do we obtain the force-constant matrices for pair of atoms located alo= ng the cube axes direction. I will be VERY VERY GRATEFUL to any help in this regard.
Sandeep K. Lahiri Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge, MA=
