Input for Second-Order Elastic Constants Analysis

Last updated

Jul 25, 2024

Author

Gianfranco Ulian

The input file for the analysis of the second-order elastic constants (SOEC) can be of any extension, albeit .dat should be preferred.

Note

No keyword is necessary for this input.

The file is a text file containing the 21 elastic constants in either upper triangular, lower triangular and complete form.

The first line is intended for a short description of the system under analysis, but it can be omitted if the user wants so. Then the six rows of the second-order elastic constants has to be supplied in Voigt’s notation.

After the elastic constants, it can be supplied the density of the crystal system, expressed as \(kg m^{-3})\). If not supplied, the seismic wave velocities will not be calculated as they require this information.

An example of the input file for hydroxylapatite (hexagonal crystal) is the following: 1

Hydroxylapatite
187.208   65.193   84.703    0.000    0.000    0.000
         187.208   84.703    0.000    0.000    0.000
                  222.658    0.000    0.000    0.000
                            39.687    0.000    0.000
                                     39.687    0.000
                                              61.007
3178

Note

A command for the automatic generation of the input file used by Quantas for the second-order elastic constants analysis of crystalline solids is provided to aid the user. However, at the moment, it is compatible only with the output files of CRYSTAL14 (and above) and VASP.

Note

New in version 0.9.1: The same input for the analysis of the second-order elastic moduli can be employed for a complete analysis of the propagation of acoustic waves in homogeneous, crystalline solids.

References

1

Ulian, G., Valdre, G. Second-order elastic constants of hexagonal hydroxylapatite (P63) from ab initio quantum mechanics: comparison between DFT functionals and basis sets, Int. J. Quantum Chem., 118 (2018) e25500.