[Pw_forum] What is the different between Born effective charge and effective

[Diep Vinh Quang]

Dear all,

Right now I am calculating the IR spectrum of Polyethylene (12 atom in a
unit cell) by using the example09. I also deal with the effective charge
and the dynamical matrix to  calculate IR. But I get the result for the
effective charge like the following (it is a tensor):
atom 1 = C
     2 = H
     3 = H
     4 = C
     5 = H
     6 = H
........


     Effective Charges E-U: Z_{alpha}{s,beta}

     atom #    1
         -0.099427475790         -0.248752090473          0.001043795428
         -0.069615072695         -0.159907527964          0.007634655521
         -0.001753156183          0.006377735929         -1.312054019801
     atom #    2
          0.077956360437         -0.030538688100          0.000934947973
         -0.199637665554         -0.046995649249          0.001576613923
         -0.000850707804          0.003202247825          0.059757957907
     atom #    3
          0.032830541054          0.147773617226          0.000600323072
          0.175304985018         -0.199147711217         -0.004431652344
          0.003510661051         -0.002839150183          0.046754448589
     atom #    4
         -0.022464377689         -0.205009989734          0.000887740549
         -0.077166162241         -0.161294181774          0.011823645473
         -0.002437562298          0.010399149740         -1.323252940006
     atom #    5
         -0.058408457609         -0.067254988611         -0.000085228083
         -0.254215018726         -0.028258016054          0.001283680975
         -0.001137843246          0.001977691596          0.058849948380
     atom #    6
          0.008147259866          0.125032673064          0.001112013451
          0.140717895758         -0.170289293702         -0.004346617517
          0.003720246553         -0.002531134573          0.059304718408
     atom #    7
         -0.102543543931         -0.249140592599          0.001444711453
         -0.071204041408         -0.156518468321          0.005522539460
          0.005068839433         -0.000136373867         -1.310914795339
     atom #    8
          0.080427330490         -0.029766382005          0.000949440595
         -0.197677260138         -0.048161049366          0.001682025760
         -0.000794687824          0.003304342703          0.060723469122
     atom #    9
          0.032606029639          0.148487590659          0.000617626001
          0.175284391800         -0.197008577608         -0.004454326407
          0.003562264841         -0.002896819928          0.047484400215
     atom #   10
         -0.023549648226         -0.204184590745          0.000862655075
         -0.076420841674         -0.158655937842          0.011795766380
          0.000669693064          0.011438938194         -1.322555094138
     atom #   11
         -0.056614516798         -0.066225081854         -0.000066149431
         -0.252832726795         -0.029751471027          0.001395607163
         -0.001131325363          0.002098938278          0.059573058213
     atom #   12
          0.007792801562          0.126138888731          0.001135706575
          0.141185264261         -0.168958178617         -0.004372196571
          0.003739948221         -0.002524338993          0.059935664421

Therefore my question is: What is the different between Born effective
charge and the above effective charge? Or are they the same? And on the
other hand, how can we impose sysmetry condition for the caculation of Z*
(sum of Z* of each atom in one direction must = zero)

Thank you in advance.

Vinh