Raman tensor output

[Jia-Lin Chang]

Hi,
I am a CRYSTAL23 user. I performed the computation of Raman intensities of some crystals. I wonder how to get the values of the Raman tensor? I read a copy of the TENS_RAMAN.DAT file, but I don't known how these data are defined. I assume that each row corresponds to a phonon mode and the columns are subsequently the xx, xy, xz, yy, yz, and zz componesnts of the Raman tensor, am I right? I found that the computed polarized Raman intensities are consistent with the space group of the crystal, but the Raman tensors are not, given the tensors are all non-zero. Can you please tell me how to get the data of Raman tensor from the output and tell me the unit of the Raman tensor CRYSTL23 used? Thanks a lot!

[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,

[Jia-Lin Chang]

​Dear Prof. Erba,

Thank you for your clear explanation.