What is the order of total energy of a unit cell (NOT SUPERCELL) of any crystal? I am finding it in ~100 eV order in some papers and ~100 KeV order in others. Maximum reports with WIEN2k calculation reports KeV oeder. Which one is correct?
based on my calculations on different phases of BeF2 and SiO2 (unit cells), I think it should be in ~100 eV or less.
Dear Santanu,
I don't think the total energy for a unit cell can ever go to 100 keV order. If it is a super cell, then also it will go little high (few 100 eV depending upon supercell size), but I don't think it will ever reach ~100keV. I have done the calculations for ZnO, MgO and SnO2, TiO2 etc using VASP software package, but I have never found energy ~100 keV. As for the software is concerned all the software (be it VASP or WIEN 2K) should give same order energy, after all, all packages are based on DFT (slight may be there, depending upon pseudo potential and correlation functional used).
If you come across some papers on the oxides (SnO2, TiO2, ZnO, MgO), please let me know. I too want to know how they have found.
Regards,
Homnath
As mentioned by Homnath, all the software (VASP or WIEN 2K or Quantum espresso) should give similar energy values for a given unit cell since all packages are based on DFT.
The energy of the unit cell obviously depends on the number of atoms in the unit cell. I have never really seen a total energy of a unit cell ~ 100 eV unless the unit cell has like 100 atoms. For example a unit cell of Nb (BCC) with 2 atoms has around ~20 eV energy for the unit cell. But, if I take a unit cell for a grain boundary of Nb in DFT (VASP) which has around 60 atoms, then my unit cell energy will be around ~600 eV for the unit cell of niobium grain boundary.
Did you get the answer, I am also in this situation only right now Santanu Pathak
The reference frame has to be considered when energy is concerned. In some literatures, the reference is not clearly mentioned and that probably makes the confusion regarding the order/ magnitude of energy. Shamili Gnanadoss