Polymorphism, phonon dynamics and carrier-phonon coupling in pentacene

The crystal structure and phonon dynamics of pentacene is computed with the Quasi Harmonic Lattice Dynamics (QHLD) method, based on atom-atom potential. We show that two crystalline phases of pentacene exist, rather similar in thermodynamic stability and in molecular density. The two phases can be easily distinguished by Raman spectroscopy in the 10-100 cm-1 spectral region. We have not found any temperature induced phase transition, whereas a sluggish phase change to the denser phase is induced by pressure. The bandwidths of the two phases are slightly different. The charge carrier coupling to low-frequency phonons is calculated.Comment: 6 pages, 3 figures. Presented at ICFPAM-

Effect of Kaolin/Defoliation Combined with Dry Ice on Lambrusco Red Wine Production to Constrain the Effects of Climate Change

Since viticulture is affected considerably by climate change, it is imperative to encourage research on newstrategies in order to constrain these critical effects on the composition of berries and the quality of wines.A multi-strategy approach composed of (i) kaolin application on foliage, (ii) late tree defoliation and (iii)cryomaceration of grapes with dry ice was evaluated in the production of Lambrusco Salamino wines.Physical, chemical and sensory analyses were carried out on the sample set, including the control wines.In general, cryomaceration with dry ice proved to be a winning choice to lower alcoholic strength (roughly5%). In addition, the wines showed an increase in anthocyanin content by approximately 17%, while thecontent of catechins, flavanols and hydroxycinnamic acids decreased. Consistent with the increase in theanthocyanin content, an increase in colour indices and sensory colour intensity scores was observed. As forthe aromatic profile, 2-phenylethanol showed an increase of approximately 18% in the treated wines while,in parallel, a lower content of C6 alcohols and volatile fatty acids was observed. The multiple adaptationstrategies put in place in the present study show an alternative way to mitigate the severe effects of climatechange on wine production, and to face changing consumer demands

Seasonal variability of the HO.RE.CA. food leftovers employed as a feeding substrate for black soldier fly (Hermetia illucens L.) larvae and effects on the rearing performance

The SCALIBUR project (Horizon, 2020) aimed to explore innovative solutions, including the use of black soldier fly larvae, for the bio-urban waste management. This research work describes the evaluation of the variability in water, proteins, fat, ashes, and carbohydrates present in the HO.RE.CA. food leftovers which were withdrawn from a local canteen over a 12-month period and the relationship with (i) the growth parameters of the larvae, (ii) the percentage of substrate reduction and the percentage of frass separated through the mechanical sieve at the end of the rearing process. HO.RE.CA. food leftovers are overall a suitable feeding substrate for larval rearing. Water contained in the HO.RE.CA. food leftovers was sufficient for larval rearing without resorting to further addition. As for water content, a seasonal trend was not observed, on the contrary, it was proved to be totally random. However, high amount of water (>80%) was correlated with higher larval mortality rate. The larval weight was significantly correlated to the amount of protein (r = 0.80; p ≤ 0.001) present in the substrate, and to a lesser extent to the amount of fat (r = 0.43; p ≤ 0.05). The feed conversion rate and bioconversion rate were both in agreement with literature data. The statistical test did not show any significant correlation between the amount of water contained in the initial fresh HO.RE.CA. food leftovers and the percentage of substrate reduction and the percentage of frass separated through the mechanical sieve at the end of the rearing process

Direct evidence of overdamped Peierls-coupled modes in TTF-CA temperature-induced phase transition

In this paper we elucidate the optical response resulting from the interplay of charge distribution (ionicity) and Peierls instability (dimerization) in the neutral-ionic, ferroelectric phase transition of tetrathiafulvalene-chloranil (TTF-CA), a mixed-stack quasi-one-dimensional charge-transfer crystal. We present far-infrared reflectivity measurements down to 5 cm-1 as a function of temperature above the phase transition (300 - 82 K). The coupling between electrons and lattice phonons in the pre-transitional regime is analyzed on the basis of phonon eigenvectors and polarizability calculations of the one-dimensional Peierls-Hubbard model. We find a multi-phonon Peierls coupling, but on approaching the transition the spectral weight and the coupling shift progressively towards the phonons at lower frequencies, resulting in a soft-mode behavior only for the lowest frequency phonon near the transition temperature. Moreover, in the proximity of the phase transition, the lowest-frequency phonon becomes overdamped, due to anharmonicity induced by its coupling to electrons. The implications of these findings for the neutral-ionic transition mechanism is shortly discussed.Comment: 11 pages, 13 figure

(Perylene)3-(TCNQF1)2: Yet Another Member in the Series of Perylene–TCNQFx Polymorphic Charge Transfer Crystals

The 3:2 Charge Transfer (CT) co-crystal (Perylene)3(TCNQF1)2 is grown by the Physical Vapor Transport (PVT) method, and characterized structurally and spectroscopically. Infrared analysis of the charge sensitive modes reveals a low degree of charge transfer (less than 0.1) between donor and acceptor molecules. The crystal is isostructural to the other 3:2 CT crystals formed by Perylene with TCNQF2 and TCNQF4, whereas such stoichiometry and packing is not known for the CT crystals with non-fluorinated TCNQ. The analysis of the isostructural family of 3:2 Perylene–TCNQFx (x = 1,2,4) co-crystal put in evidence the role of weak F…HC bonding in stabilizing this type of structure</jats:p

BEDT-TTF organic superconductors: the entangled role of phonons

We calculate the lattice phonons and the electron-phonon coupling of the organic superconductor \kappa-(BEDT-TTF)_2 I_3, reproducing all available experimental data connected to phonon dynamics. Low-frequency intra-molecular vibrations are strongly mixed to lattice phonons. Both acoustic and optical phonons are appreciably coupled to electrons through the modulation of the hopping integrals (e-LP coupling). By comparing the results relevant to superconducting \kappa- and \beta-(BEDT-TTF)_2 I_3, we show that electron-phonon coupling is fundamental to the pairing mechanism. Both e-LP and electron-molecular vibration (e-MV) coupling are essential to reproduce the critical temperatures. The e-LP coupling is stronger, but e-MV is instrumental to increase the average phonon frequency.Comment: 4 pages, including 4 figures. Published version, with Ref. 17 corrected after publicatio

Effect of Benzoic Acids on Barite and Calcite Precipitation

The effect of various benzoic acids on the precipitation of barite (BaSO4) and calcite (CaCO3) was investigated. The acids varied in the number of carboxylate groups, from dibenzoic acids (phthalic, isophthalic, and terephthalic) through to the hexabenzoic acid (mellitic acid). It was found that the stereochemistry of the dibenzoic acids was important, as was the pH of the solution (trimesic acid was used as a test case and showed that greatest inhibition was achieved with all carboxylate groups deprotonated). Interestingly, for both the calcite and barite systems, mellitic acid was found to be both a potent inhibitor and a significant crystal growth modifier. In the case of barite, the presence of mellitic acid produced nanoparticles that agglomerated. The nanoparticles were found to be 20 nm in size from X-ray diffraction (XRD) line width analysis and 20-50 nm from transmission electron microscopy (TEM). Humic acid was also tested and found to form bundled fibers of barium sulfate