Single crystals of L‐alanine have been grown from buffered aqueous solutions and characterised as to their optical quality via wavefront distortion analysis, electrooptical response and harmonic generation efficiency. Refraction indices as well as phase matching loci were found in satisfactory agreement with previously published data for crystals grown in non buffered solution. Estimates for the electro‐optical response are reported for the first time. The experimentally observed crystal habit is discussed in terms of morphological importance (M.I.), which was found to be in disagreement with the predictions of crystallographic criteria based on the interplanar distance dhkl, on the periodic bond chains (PBC) and the attachment energy Eatt. This disagreement is tentatively attributed to the presence of impurities and non‐appropriate supersaturation conditions.
A new growth method, based on a vapour-liquid-solid (VLS) mechanism, is reported for preparing single crystals of N-methylurea (NMU), a material which appears to be a good alternative to urea for non-linear optical applications in the "near UV-visible" region of the spectrum. Details of the growth procedure are given and it is shown that large single crystals, with volumes up to 7 f 10 cm3, can be obtained with satisfactory reproducibility and very fast growth rate. Structural and optical characterisation, still preliminary, are reported, which evidence a crystalline quality comparable to that of urea and N-methylurea as previously grown with other growth techniques
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