Pressure-induced changes in parameters of the indicatrix of lithium sodium sulfate crystals

Spectral, temperature, and baric dependences of birefringence $\Delta n_{i}$ of LiNаSO$_{4}$ (LSS) crystals have been studied. It is established that dispersion $\Delta n (\lambda)$ is anomalous. It is shown that uniaxial compression leads to changes in $\Delta n_i$ with different magnitudes and signs. The dispersion effect of changes in $\Delta n_i$ decreases under stress $\sigma\perp z$ and increases in the opposite case $(\sigma\parallel z)$. Pressure-induced changes in the refractive index are estimated; it is established that the refractive indices of an LSS crystal increase under uniaxial compression, which may be related to compression of the crystal and change in its interatomic bond nature.