Crystals frustrated lattices

The frustration effects are implicit in many physical systems, as different as spin glass magnets, adsorbed monomolecular films and liquid crystals [32, 54, 55], In the case of polar mesogens the dipolar frustrations may be modelled by a spin system on a triangular lattice (Fig, 5), The corresponding Hamiltonian consists of a two particle dipolar potential that has competing parallel dipole and antiparallel dipole interactions [321, The system is analyzed in terms of dimers and trimers of dipoles. When the dipolar forces between two of them cancel, the third dipole experiences no overall interaction. It is free to permeate out of the layer, thus frustrating smectic order. 

NMR is a powerful technique for providing information about the distribution and dynamics of local RFs, characteristic of such systems. While the quadrupole-perturbed NMR line shape analysis gives details about the distribution of local RFs, spin-lattice relaxation (SLR) studies can give information on the dynamics in the frustrated state of these systems. From the literature, it can be seen that most of the NMR experiments have been carried out in RADP mixed systems and its deuterated analogues. ETFI group published a number of results21-23 on various mixed crystals. 

B. Zappone, C. Meyer, L. Bruno, E. Lacaze, Periodic lattices of frustrated focal conic defect domains in smectic liquid crystal films. Soft Matter 8, 4318 326 (2012)... 

It is quite natural to link robusmess to bond strength, and strong hydrogen bonds have the potential to override the multitude of other intermolecular forces in the crystal lattice (e.g., van der Waals, dipole-dipole, multipolar) that otherwise can frustrate rational crystal design. On the other hand, modifications to the backbone of n-dimensional networks naturally will alter packing requirements, whether within the network or between pendant substituents, which could exert strain on the network. Consequently, networks may be more robust if they are somewhat... 

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