Intermolecular Interactions in Molecular Organic Crystals upon Relaxation of Lattice Parameters

First-principles intermolecular binding energies in organic molecular crystals

The intermolecular binding (lattice) energies are calculated for the molecular crystals cyclotrimethylene trinitramine, pentaerythritol, and pentaerythritol tetranitrate using the CRYSTAL 98/03 and GAUSSIAN 98 programs, the DMOL program and the CASTEP program and compared with experiment. Calculating the theoretical intermolecular binding energy as a tool for testing the intrinsic quality of a ...

Variation of intermolecular interaction and local lattice distortion of parahydrogen crystals upon vibrational excitation

When a hydrogen molecule in a parahydrogen crystal is excited to a high vibrational overtone state, its electronic properties vary significantly since the energy of excitation is a sizable fraction of the energies of the excited electronic states. Thus the vibrational excitation leads to a significant variation of the intermolecular potential and resultant local distortion of the crystal lattic...

The Spin Lattice Relaxation of the Nuclear Dipolar Energy in Some Organic Crystals with Slow Molecular Motions

The relaxation of nuclear dipolar energy to the lattice has been measured in three different organic solids (benzene, cyclohexane and hexamethylbenzene) as a function of temperature. In the cases of C6H8 and C 6 (CH 3 ) 6 very slow motions associated with rather high activation energy were detected near the melting point. They are thought to be thermally activated rotations of the molecules abo...

NQR Studies of Phase Transitions and Intermolecular Interactions in Crystals*

Simple methods to analyze the anomalous behavior o f NQ R parameters are presented. Unusual positive temperature coefficients o f antimony resonance frequencies in (N H 4)2SbF5 below the phase transition at 169 K were interpreted in terms o f ordering processes o f the ammonium ions. Calculation o f the EFG in LaF3 revealed that the translational diffusion of Li ions brings about an anomalous d...

Excitons in Organic Molecular Crystals