An issue with your input is that you place the point where the external saw-tooth potential has a discontinuity in its derivative at emaxpos = 0.5 (it is in crystal units, so because edir = 3, it means that the potential depends on z and the discontinuity is at (0,0,a/2)). However, the CO2 molecule is placed along the x axis at fixed y = a/2 and z = a/2. As such, the discontinuity, which is unphysical since in serves to compensate the spurious dipole field that would arise as a consequence of the periodic boundary conditions, is located in a region where the charge density is not zero. emaxpos should be set in such a way that the discontinuity il located in the vacuum, in the region where the charge density is zero or in any case very small. In your setup it seems that a good choice would be emaxpos=0.
Giovanni PS since you’re studying an isolated molecule, provided the size of your supercell is sufficiently large, the eigenvalues should exhibit no dependence on k. As a consequence, in this case, a 4x4x4 sampling of the Brillouin zone, should provide results equivalent to a gamma only sampling. So, you can switch to KPOINTS automatic 1 1 1 0 0 0 or, even better, KPOINTS gamma to make your calculation faster while keeping the same accuracy. > On 27 May 2020, at 03:42, ENDALE ABEBE <end...@gmail.com> wrote: > > Dear Experts, users and all > > I found the dipoles of CO2 calculated by Quantum ESPRESSO as : > > Computed dipole along edir(3) : > Elec. dipole 0.3112 Ry au, 0.7909 Debye > Ion. dipole 0.8137 Ry au, 2.0683 Debye > Dipole 41.9812 Ry au, 106.7055 Debye > Dipole field 0.5025 Ry au, > > I assumed the third value is the sum of the electronic and ionic > contributions. > The input and output files are attached herewith. > Since CO2 is non-polar molecule (with polar bonds), shouldn't the total > dipole moment be zero? > > -- > Endale Abebe > Program coordinator and Lecturer > Faculty of Materials Science and Engineering > Jimma Institute of Technology > Jimma University > P.O.Box 378, Jimma, Ethiopia > Mobile: +251921381598 > <CO2_nscf.out><CO2_nscf.in>_______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: giovanni.cant...@spin.cnr.it gcant...@gmail.com Phone: +39 081 676910 Skype contact: giocan74 Web page: https://sites.google.com/view/giovanni-cantele
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