Single structural data

However, its was found possible to infer all four microscopic tensor coefficients from macroscopic crystalline values and this impossibility could be related to the molecular unit anisotropy. It can be shown that the molecular unit anisotropy imposes structural relations between coefficients of macroscopic nonlinearities, in addition to the usual relations resulting from crystal symmetry. Such additional relations appear for crystal point group 2,ra and 3. For the monoclinic point group 2, this relation has been tested in the case of MAP crystals, and excellent agreement has been found, triten taking into account crystal structure data (24), and nonlinear optical measurements on single crystal (19). This approach has been extended to the electrooptic tensor (4) and should lead to similar relations, trtten the electrooptic effect is primarily of electronic origin. 

SCHEME 14.5 Different synthetic routes for the preparation of metallacyclocumulene (5). Note The perception of strain energy in the cyclocumulene is so high that initial attempts at publishing the experimental single crystal data of the metallacyclocumulene (5) met with strong resistance from referees (personal comments from Prof. U. Rosenthal). Characterization of the structure computationally helped in gaining acceptance of the structure. 

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