The behavior of silicalite-1 under high pressure conditions studied by computational simulation

Completely siliceous zeolite ZSM-5 (silicalite-1) under high external pressures, up to 7 GPa, was investigated by energy minimization techniques. Classical empirical potentials have been used to study the phase transformation of the silicalite crystal to a new one with a lower symmetry. The analysis of the unit cell geometry and vibrational spectra at selected pressures suggest the loss of crystallinity of the silicalite structure. We found that a low-density amorphous phase is reached at pressures around 2.5–3.5 GPa. These results are compatible with recent Raman and X-Ray diffraction studies. We report the structural and vibrational properties of the new phase. In addition, we report the simulated elastic constants and the Young’s modulus of silicalite at selected pressures. The simulated results are in semi-quantitative agreement with the experiment.