It doesn’t happen often. Simply marking for interested parties that David Bradley wrote a piece about the recent L-Alanine Alaninium Nitrate article published in Physical Chemistry Chemical Physics (Phys. Chem. Chem. Phys., 2009, 11, 9474 – 9483, DOI: 10.1039/b905070a) with a specific focus on the organic ferroelectric behavior of this system as argued from the results of the inelastic neutron scattering (INS) and temperature-dependent Raman spectroscopic studies. Also, of course, the entire discussion and analysis revolves around the results of the density functional theory (DFT) studies performed on the solid-state system with DMol3.
I find it mildly amusing that a paper that went through several rather exhaustive crystallography-focused review cycles (fighting with crystallography-specific reviewers about the use of the vibrational spectroscopy to provide the more realistic view of this organic salt in the solid-state) makes headlines (well, you know) only for the vibrational spectroscopy. I certainly won’t point fingers (only browsers), but I’ve yet to see someone say the same of vibrational spectroscopists.
As a brief addition, the Raman spectrum presented on the spectroscopyNOW website does not provide quite the resolution of the original. In the interest of laying all doubts aside, a larger version of the same image is provided below.
The 293 K and 78 K Raman spectra of LAAN showing temperature-dependent peak changes (black box).
According to the article (his, not ours)…
Even if there turns out to be no ferroelectric transition in LAAN, it could still represent an unusual and intriguing structure in which both a neutral and zwitterionic L-alanine amino acid exist in the same crystal cell together with crystalline nitric acid. Such a material might help to improve the computational structural models, improve our understanding of the spectra of related materials and perhaps offer clues to designing a next-generation material that does have the elusive ferroelectric properties.
The article is available at www.spectroscopynow.com/coi/cda/detail.cda?id=22458&type=Feature&chId=3&page=1. A local copy of the article (in PDF format) is here: 2009december1_spectroscopynow_organicferroelectrics.pdf