Posts

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  BETAVIB (Vibrational contribution to the SHG and Electro Optic-Effect)
  undefined aerba

  Excellent, thank you for the quick feedback.

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  BETAVIB (Vibrational contribution to the SHG and Electro Optic-Effect)
  undefined aerba

  Hi,

  We have checked the implementation. The values printed in the output of the BETAVIB calculation for SHG and Pockels are expressed in atomic units and correspond to \( \frac{1}{2}{\boldsymbol{ \beta}} \). That is, the factor of \( \frac{2\pi}{V} \) seems to be missing to make them the d tensor. In other words, by multiplying the values in the output by \( \frac{2\pi}{V} \) you should get d.

  Please, let me know if you think this makes sense based on the values you get for your system.

  Sorry for the confusion.
  Hope this helps,

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  D3 correction not working for some functionals with the use of DFTD3 section
  undefined ldona

  Dear leszec_malec,

  You can bypass the error by using a functional parameterized for DFT-D3 (BJ), for example PBE, and then manually defining the dispersion parameters.

  Please see the DFTD3 block below:

  DFTD3
  VERSION
  4
  FUNC
  PBE
  S6
  1.0000
  S8
  1.6112
  A1
  0.0000
  A2
  7.3539
  END
  

  Best regards,

  Lorenzo

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  Stability calculations
  undefined aerba

  Formally, if finite temperature effects are to be included, the internal static energy E needs to be substituted with the free energy F in the definition of the Hessian. This is easier said than done. However, for the elastic tensor, we do have an implementation to compute free energy derivatives with respect to lattice strain (i.e. thermo-elasticity). See also:

  https://www.mdpi.com/2075-163X/9/1/16

  The elastic tensor is not defined for 0D systems, where you could just explore the "dynamical stability" in terms of the vibration frequencies.

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  Stability calculations
  undefined aerba

  Hi,

  Stability is a broad concept that can be interpreted and analyzed in many ways. One way to look at it is the following: checking whether or not the Hessian of second energy derivatives is positive-definite (all eigenvalues are positive) or not, i.e. if the structure is a local minimum of the potential energy surface (PES). Indeed if small structural perturbations produce an energy decrease rather than increase (that is if some of the eigenvalues are negative) the structure can not be considered "stable".

  Two types of Hessian matrix can be considered, which correspond to two types of stability:

  • Hessian with respect to atomic displacements within a fixed cell for dynamical (phonon) stability. This corresponds to checking if all harmonic frequencies are positive.

  • Hessian with respect to lattice distortions for mechanical stability (so-called Born stability conditions). This corresponds to checking if all the eigenvalues of the elastic tensor are positive.

  Hope this helps,

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  Creating Wannierization Input Files
  undefined GiacomoAmbrogio

  Hi Chris,
  I tested the same input with properties and it starts correctly, so the input deck itself seems fine. The issue may instead be that the launch script that is not pointing to the correct input file.

  Without your fort.9 I cannot test the full input, but if you share a few details on your setup and how you launch the job, it may be easier to identify the problem.

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  Localized Crystalline Orbitals
  undefined GiacomoAmbrogio

  Dear Chhatra,

  Unfortunately, I am not aware of a direct way to reduce the file size generated by the ORBITAL option in the properties module.

  As a possible workaround, you might consider reducing the system size if feasible. Another option could be to post-process the output to extract only the relevant information before visualization.

  I hope this helps.

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  BETAVIB (Vibrational contribution to the SHG and Electro Optic-Effect)
  undefined aerba

  Hi,

  Could you please share your CRYSTAL output file from the BETAVIB calculation? In case you also computed just the electronic term, could you share those output files as well?

  The first link you give looks broken: 404 page not found.
  Thanks,

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  Localized Crystalline Orbitals
  undefined GiacomoAmbrogio

  Hi Chhatra,
  the last 1 in the second line of the NEWK input

  NEWK
  3 3
  1 1  <--- this one
  67 501
  ...
  

  is the number of printing options to switch on (as stated in the manual).

  Thus, the following line contains the number of the print option (67: eigenvectors of the Fock - see the LPRINT appendix in the manual) and the value of that print option (501: number of vectors to print)

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  Troubles with coordinate system in output using POTC
  undefined GiacomoAmbrogio

  Hi denkos,
  From what I can see in the code, the components are not sorted automatically. CRYSTAL just diagonalizes the EFG tensor and prints the three eigenvalues as AA, BB, CC with their corresponding eigenvectors.