Compression behavior of energetic ε‐CL‐20 crystals from density functional theory calculations.

Using dispersion corrected density functional theory, we comprehensively explore the structure and the Raman spectra of hexanitrohexaazaisowurtzitane (CL‐20) crystal under hydrostatic and uniaxial compression. Through hydrostatic compression, we verify that PBE‐D2 scheme can accurately describe the crystal structure under zero pressure and high pressure. Along different orientation compressions, the CL‐20 crystal exhibits considerable anisotropy in principal stresses and shear stresses. The compression effects on the vibration properties of CL‐20 are further analyzed. Compression along the [100] orientation induces some anomalous changes for vibrational modes of the nitro groups, which are associated with changes of the spatial orientation of the nitro groups. This work is expected to shed light on the anisotropic behavior and pressure‐induced configurations transitions of CL‐20 at atomistic scale. [ABSTRACT FROM AUTHOR]