Discussion Comment on the paper by M. Lenin, G. Bhavannarayana, P. Ramasamy ‘‘Synthesis, growth, and characterization of a non-linear optical crystal – glycine lithium chloride” Opt. Commun. 282 (2009) 1202 Michel Fleck a, * , Aram M. Petrosyan b a Universität Wien – Geozentrum, Institut für Mineralogie und Kristallographie, Althanstraße 14, A-1090 Wien, Austria b Molecule Structure Research Center NAS of Armenia, 26 Azatutyan Ave., Yerevan 0014, Armenia article info Article history: Received 15 February 2009 Accepted 24 July 2009 abstract We argue that the ‘‘glycine lithium chloride” crystal grown and characterized in the title paper actually is gamma glycine. Ó 2009 Elsevier B.V. All rights reserved. The authors of the title paper [1] have presented their data and conclusions in the belief that they obtained glycine lithium chlo- ride. Since the obtained crystal is assumed to be known (the authors even quoted Ref. [2]) it would be natural to identify the ob- tained crystal by comparing its unit cell parameters with those published previously, i.e., in [2] or other literature on similar com- pounds (e.g., [3] and references therein). However, the authors did not compare the measured unit cell parameters with those reported previously in any way, although the crystal presented in [2] is absolutely different from that grown in [1]. The species reported in [2] has the chemical composition (C 2 H 5 NO 2 )ÁLiClÁH 2 O and is characterized by the following crystallo- graphic parameters: monoclinic, space group P2 1 /c, a = 10.103 (2) Å, b = 5.064 (1) Å, c = 11.930 (2) Å, b = 107.39 (1)°, Z = 4. If the authors [1] considered that they have obtained a new species in the system glycine – LiCl – water, i.e., an anhydrous form, then it would have been necessary to note this circumstance particularly and discuss the differences to the monohydrate in detail. Con- trarily, the authors do not present any crystal structure, just the unit cell parameters (a = b = 7.023 Å, c = 5.478 Å, c = 120°) without any discussion. Moreover, the X-ray powder diffractogram shown in the paper is certainly not from any crystal species with the given unit cell parameters. From various earlier studies on crystals composed of glycine and alkali halogenids, it is known that the addition of NaCl and KCl to aqueous solutions of glycine promotes the formation of gamma gly- cine [4,5], which has the following unit cell parameters: a = 7.037 Å, b = 7.037 Å, c = 5.478 Å, c = 120°, space group P3 2 [6]. These param- eters are fairly close to those reported for ‘‘glycine lithium chloride” (a = b = 7.023 Å, c = 5.478 Å, a = b = 90°, c = 120°), especially when considering the fact that the authors did not give any e.s.d.’s. This also proves that the X-ray powder diffractogram shown in the paper cannot be correct: Because of the similarity of the unit cell parame- ters of ‘‘glycine lithium chloride” [1] and gamma glycine [6], the reflections should be at similar 2-theta values, which they are not (compare with the X-ray powder diffractogram of gamma glycine in the PDF [7]). Also, it is questionable why the (0 0 5) reflection should be that prominent, or if it could be there at all (in the space group gamma glycine crystallizes in, P3 2 , this reflection is systemat- ically absent). From all the data, the conclusion arises that the crystal obtained in [1] is gamma glycine. A comparison of the IR spectrum shown in [1] with the IR spectrum of gamma glycine shows their complete coincidence and confirms their identity. References [1] M. Lenin, G. Bhavannarayana, P. Ramasamy, Opt. Commun. 282 (2009) 1202. [2] G. Müller, G.-M. Maier, M. Lutz, Inorg. Chim. Acta 218 (1994) 121. [3] M. Fleck, K. Schwendtner, A. Hensler, Acta Cryst. C62 (2006) m122. [4] K. Ambujam, S. Selvakumar, D. Prem Anand, G. Mohamed, P. Sagayaraj, Cryst. Res. Technol. 41 (2006) 671. [5] T. Balakrishnan, R. Ramesh Babu, K. Ramamurthi, Spectrochim. Acta. A 69 (2008) 1114. [6] Y. Iitaka, Acta Cryst. 14 (1961) 1. [7] PC-PDF, Powder Diffraction File: International Centre for Diffraction Data (JCPDS/ICDD), Newton Square, PA 19073, USA, 1999–2000. 0030-4018/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2009.07.056 * Corresponding author. E-mail address: michel.fleck@univie.ac.at (M. Fleck). Optics Communications 282 (2009) 4378 Contents lists available at ScienceDirect Optics Communications journal homepage: www.elsevier.com/locate/optcom