Posts

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  Raman tensor output
  undefined aerba

  Hi,

  Indeed, columns of the TENS_RAMAN.DAT file correspond to xx, ..., zz components of the polarizability tensor \( \alpha \). However, rows correspond to the 3N atomic Cartesian displacements. Indeed, the Raman tensor reported in this file corresponds to the following quantity:
  $$
  R_{ac,ij} = \frac{\partial^3 E}{\partial u_{a,c} \partial \varepsilon_i \partial \varepsilon_j} = \frac{\partial \alpha_{ij}}{\partial u_{a,c} }
  $$
  where \( \varepsilon_i \) is a Cartesian component of the electric field, and \( u_{a,c} \) is an atomic displacement of atom \( a \) along the \( c\)-th Cartesian direction. The values are reported in atomic units.

  Hope this helps,

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  Options to print KS potential
  undefined aerba

  Hi,

  With CRYSTAL (from the PROPERTIES module actually) one can output the Hartree+EN potential in the all-electron case in 2D or 3D grids with POTM and POT3 keywords, respectively. In the latter case, the output is in .cube format. But I am afraid that currently there is no keyword to plot the XC part of the potential on a grid.

• ---

  Plotting band-decomposed charge density (CBM/VBM) for 2D Janus monolayer
  undefined aerba

  Hi,

  You can do this using the PROPERTIES module. The PBAN option [see CRYSTAL23 User's Manual at page 348] allows you to build a density matrix from a user-defined subset of electronic bands. This partial density matrix is used for subsequent calculations. The ECH3 option can then be used to evaluate the associated electron density on a user-defined 3D grid of points, to be stored in .cube format, which can then be plotted in 3D isosurfaces with standard visualizers, such as VESTA.

  A template .d3 PROPERTIES input file for this would look something like:

  NOSYMADA
  NEWK
  24 24
  1 0
  PBAN
  1
  14
  ECH3
  80
  RANGE
  -10 10
  END
  

  where in PBAN as an example I have selected just 1 band, number 14 in the list.

  Hope this helps,

• ---

  Advanced School on Quantum Modelling of Materials with CRYSTAL - Volta Redonda
  undefined aerba

  It was a great week! Let me share a group picture from the event:

  

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  Question about units of "total atomic spins"
  undefined aerba

  Hi,

  If I am not mistaken, "total atomic spins" are indeed reported in units of the Bohr magneton and are obtained from a Mulliken partitioning of the spin density (i.e. difference between the electron density of spin-up and spin-down electrons).

  Cheers,

• ---

  CRYSTAL – “***********” in Sum Tensor of Vibrational Contributions to Static Polarizability (Raman, CNT 26,0)
  undefined GiacomoAmbrogio

  Hi Drmajouri2025,
  When performing frequency calculations, it is essential that the geometry is fully optimized with the SCF properly converged. If the structure is not at a true stationary point of the potential energy surface, the computed second derivatives (Hessian) can lead to unreliable frequencies and response properties.

  Regarding the *******************, these typically means that the value exceeds the field width allocated in the printing format. In other words, the number is too large (or not representable) within the fixed output format, so it is replaced by stars.

  However, in your case, since the geometry did not converge properly, the appearance of stars is very likely due to numerical problem rather than just a harmless formatting issue.

  I would strongly recommend:

  • First ensuring tight SCF convergence (you can also increse TOLDEE and/or TOLINTEG parameters).
  • Fully optimizing the geometry until forces are below the required thresholds.
  • Verifying that the optimized structure has no imaginary frequencies.
  • Only then performing the Raman calculation.

• ---

  How use CRYSTALpytools?
  undefined dmitoli

  Dear user,
  as noted by GiacomoAmbrogio, we invite you to use CRYSTALClear, which is the Python framework that we currently maintain and support. Regarding your question, yes: you should use BAND.DAT as the *.BAND file and OUTPUT as the *.out file.

• ---

  How use CRYSTALpytools?
  undefined GiacomoAmbrogio

  Hi,
  I suggest you to use CRYSTALClear instead. Here you can find an installation guide, and on the GitHub page there is the documentation and some example notebooks that you can use as template.
  For any question related to CRYSTALClear there is a dedicated section here on the forum.

• ---

  malloc during BOLTZTRA (Pproperties)
  undefined aerba

  Hi,

  We have run some tests and we have identified the origin of the problem. The calculation fails in the evaluation of the Fermi energy in the NEWK option (so before getting to the BOLTZTRA step) because of large memory requirements due to a very large number of k-points being asked and because of the replicated-memory parallel implementation of that bit of code.

  In that part of the code, with Pproperties (parallel version), data are replicated in memory by each process.

  We have run tests on this system in parallel with different number of processes (on a computing node with 128 CPU cores) and for different shrinking factor parameters of the NEWK keyword. Results are summarized in the table below:

  

  "ok" marks combinations for which the calculation run without errors. The trend is clear and can be rationalized as follows:

  • reducing the number of k points reduces memory requirments
  • reducing the number of MPI processes effectively increases the available memory/process

  Hope this clarifies things and helps find a way forward,

• ---

  How to obtain the irreducible representations of the electronic bands ?
  undefined aerba

  Hi,

  I used space group 186 for ZnO that corresponds to the one you mention. In the character table printed by CRYSTAL only those irreps that are actually used to build symmetry-adapted Bloch functions are shown. I have updated my original post above to show the irrep labels in the character tables, which match those found in the printing of the eigenvalues.

  Hope this clarifies things,