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["张�s" <zhangting1980323@gmail.com>]

Dear abinit users:

     I'd like to investigate transport electrons under high bias voltage interacting with phonons in CNT, so I should calculate the el-ph matrix elements g(k,k+q).  I've read the routine nmsq_gam.F90, and understood its meaning in principle.  By modifying it, I got the mediate result matrix gkk_qpt_tmp and the gkq_1band output, and these two matrix are related with:

              gkk_qpt_tmp = eigvec * gkq_1band * eigvec+

     I got puzzled for this representation. The gkq_1band matrix is already multiplied with reduced phonon displacement matrix displ_red,  and  what's the meaning of  this multiply-again operation? Is it an unit transform? 
     Also, when I check these two gkk matrix, I found that the gkq_1band satisfies the symmetry induced selection rule while gkk_qpt_tmp does not. For example, for a (5,5) CNT, phonon mode 60 at Gamma point is with A1g representation of D10h group, and related el-ph scattering selection rule is that intraband scattering should be allowed and interband scattering should be forbbiden. In gkq_1band, this selection rule is well satisfied( means that gkq_1band(ib1,ib1,ibranch=60,q=3*
0.0) is much larger than gkq_1band(ib1,ib2,ibranch=60,q=3*0.0)), while in gkk_qpt_tmp, which is multiplied with eigvectors of phonon,  the  result is  just  opposite,  gkk_qpt_tmp(ib1,ib1,ibranch=60,q=3*0.0) is  much  smaller  than  other  elements.  What's wrong with my  understanding?  Can someone give me some  advice? Thanks! 


Regards

                                                                  Zhang Ting
                                                                  Peking Univ.
                                                                  Nov, 19th, 2007