We present a comprehensive study of the hydrostatic pressure dependence of the vibrational properties of tetracene using periodic density-functional theory (DFT) within the local density approximation (LDA). Despite the lack of van der Waals dispersion forces in LDA we find good agreement with experiment and are able to assess the suitability of this approach for simulating conjugated organic molecular crystals. Starting from the reported Xray structure at ambient pressure and low temperature, optimised structures at ambient pressure and under 280 MPa hydrostatic pressure were obtained and the vibrational properties calculated by the linear response method. We report the complete phonon dispersion relation for tetracene crystal and the Raman and infrared spectra at the centre of the Brillouin zone.The intermolecular modes with low frequencies exhibit high sensitivity to pressure and we report mode-specific Grüneisen parameters as well as an overall Grüneisen parameter γ=2.8.Our results suggest that the experimentally reported improvement of the photocurrent under pressure may be ascribed to an increase in intermolecular interactions as also the dielectric tensor.2

The control of non-radiative losses in light-emitting diodes (LEDs) based on metal halide perovskites is crucial to improve device efficiency. Recent studies have shown a correlation between lattice strain and...

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