This article aims to highlight the importance of the link between Bologna and Barcelona, consisting of an epistemic and methodological convergence in the approach to the criminal question and, in ...particular, to the problem of penal selectivity. If on the one hand this link cannot be eliminated, on the other it is exposed to a series of attempts at obfuscation by the dominant legal and criminological ideology, which is even reflected in autobiographical contingencies that add an anecdotal dimension to the discussion. At the same time, the recovery of this link imposes a reflection on the contemporary criminological debate, since the distinctive features of Italian-Iberophone critical criminology clash with some premises of the most recent and advanced trends in terms of critical potential, in particular the zemiological approach. One example is the role that criminal dogmatics plays within the sociological analysis of the penal system following Franco Bricola’s lesson, and the meaning of this methodological choice in terms of transdisciplinarity and political radicalism. Our conclusion is that a better coordination between critical traditions is needed: one that aims at overcoming linguistic barriers and starts with a systematic review of the existing critical arsenal before any headlong rush
Recent years have witnessed an explosion of interest in predictive policing, with a clear opposition emerging between supporters and critics of its implementation. While critical accounts ...conventionally centre on opacities and operational asymmetries of the algorithmic construct (biased training, feedback loop, etc.), I argue that a different critique is first needed. Focussing on place-based techniques, I maintain that contemporary predictive mapping basically perpetuates the political and epistemic dictates which have historically framed the conceptualisation of crime in relation to space. Through a review of sources spanning from the Cartographic School to current predictive policing literature, I identify two main conceptual axes which operationalise this heritage: first, an explanatory framework of crime that has never detached from the socio-economic deficit archetype; and secondly, an ontologisation of crime alternative to biologicist positivism, nonetheless integral to the etiologic paradigm. Therefore, without first disputing these ideological bottlenecks, no initiative towards a transparent use of predictive policing is plausible, neither does a sharp distinction between place-based and person-based predictions seem tenable.
Analysis of the chemical bonding in the position space, instead of or besides that in the wave function (Hilbert) orbital space, has become increasingly popular for crystalline systems in the past ...decade. The two most frequently used investigative tools, the Quantum Theory of Atoms in Molecules and Crystal (QTAIMAC) and the Electron Localization Function (ELF) are thoroughly discussed. The treatment is focussed on the topological peculiarities that necessarily arise from the periodicity of the crystal lattice and on those facets of the two tools that have been more debated, especially when these tools are applied to the condensed phase. In particular, in the case of QTAIMAC, the physical and chemical significance of the bond paths for the very weak or the supposedly repulsive interactions, the distinctive features and the appropriateness of the several schemes that have been proposed to classify chemical bonds, and, finally, the relative importance of the local and integrated electron density properties for describing intermolecular interactions. In the case of the ELF, particular attention is devoted to how this function is formulated and to the related physical meaning, and to how can the ELF be chemically interpreted and properly analysed in crystals. Several examples are reported to illustrate all these points and for critically examine the answers obtained and the problems encountered. The discussed examples encompass the case of molecular crystals, Zintl phases, intermetallic compounds, metals, supported and unsupported metal-metal bonds in organometallics, ionic solids, crystal surfaces, crystal defects, etc. Whenever possible joint ELF and QTAIMAC studies are considered, with particular emphasis on the comparison of the bond description afforded by the ELF and the Laplacian of the electron density. Two recently proposed functions, the Localized Orbital Locator (LOL) and the Source Function in its integrated or local form are also presented, in view of their potential interest for stud ies of chemical bonding in crystals. The use of approximated ELF and LOL, as derived from the density functional form of the positive kinetic energy density, is also discussed.
A 2D map is created for solid‐state materials based on a quantum‐mechanical description of electron sharing and electron transfer. This map intuitively identifies the fundamental nature of ionic, ...metallic, and covalent bonding in a range of elements and binary compounds; furthermore, it highlights a distinct region for a mechanism recently termed “metavalent” bonding. Then, it is shown how this materials map can be extended in the third dimension by including physical properties of application interest. Finally, it is shown how the map coordinates yield new insight into the nature of the Peierls distortion in phase‐change materials and thermoelectrics. These findings and conceptual approaches provide a novel avenue to tailor material properties.
A 2D map, based on quantum‐mechanical indicators for electron sharing and transfer, intuitively classifies the fundamental bonding mechanisms in solid‐state materials. It also confirms metavalent bonding as one of the fundamental mechanisms. Extending this map in the third dimension makes it possible to include properties of application interest, and it can therefore open up a new route for computational materials design.
Modern Charge-Density Analysis focuses on state-of-the-art methods and applications of electron-density analysis. It is a field traditionally associated with understanding chemical bonding and the ...electrostatic properties of matter. Recently, it has also been related to predictions of properties and responses of materials (having an organic, inorganic or hybrid nature as in modern materials and bio-science, and used for functional devices or biomaterials).Modern Charge-Density Analysis is inherently multidisciplinary and written for chemists, physicists, crystallographers, material scientists, and biochemists alike. It serves as a useful tool for scientists already working in the field by providing them with a unified view of the multifaceted charge-density world. Additionally, this volume facilitates the understanding of scientists and PhD students planning to enter the field by acquainting them with the most significant and promising developments in this arena.
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► The reduced density gradient (RDG) is used to study non-covalent interactions (NCIs). ► X-ray vs Independent Atom Model (IAM) charge density NCI pictures are contrasted. ► The two ...pictures generally reveal the presence of the same interactions. ► NCI information at the IAM level is much less detailed and chemically meaningful. ► Use of the simpler RDG–IAM approach to study NCI in complex systems is questioned.
The novel non-covalent interaction (NCI) descriptor proposed by Johnson et al. (J. Am. Chem. Soc. 2010, 132, 6498–6506) and based on the reduced density gradient (RDG), is applied to three molecular crystals, spanning a wide range of NCI classes. The key-aspect of this work is to contrast the NCI description obtained using the RDG of the electron density (ED) derived from single-crystal X-ray diffraction data with that calculated from the RDG of the corresponding Independent Atom Model (IAM) density. It is shown that the RDG isosurfaces obtained from the simpler, unperturbed model density are often able to highlight the same interactions revealed by the corresponding surfaces using the crystalline density, but differ systematically in size and are generally much less structured than these latter. A qualitative rationale for such differences is provided for the first time. Our results question the use of the simpler density model to study NCI in large biological systems.
Non‐covalent interactions (NCI) define the rules underlying crystallisation, self‐assembly and drug–receptor docking processes. A novel NCI descriptor, based on the reduced electron density gradient ...(RDG), that enables easy visualisation of the zones of the electron density (ED) involved in either the supposedly attractive (dispersive, hydrogen bonding) or allegedly repulsive (steric) intermolecular interactions, was recently developed by Johnson et al. Here, it is applied for the first time to EDs derived from single‐crystal X‐ray diffraction data. A computer code handling both experimental and ab initio EDs in the RDG‐NCI perspective was purposely written. Three cases spanning a wide range of NCI classes were analysed: 1) benzene, as the prototype of stacking and weak CH⋅⋅⋅π interactions; 2) austdiol, a heavily functionalised fungal metabolite with a complex hydrogen‐bonding network; 3) two polymorphs of the heteroatom‐rich anti‐ulcer drug famotidine, with van der Waals and hydrogen‐bond contacts between N‐ and S‐containing groups. Even when applied to experimental EDs, the RDG index is a valuable NCI descriptor that can highlight their different nature and strength and provide results of comparable quality to ab initio approaches. Combining the RDG‐NCI study with Bader’s ED approach was a key step forward, as the RDG index can depict inherently delocalised interactions in terms of extended and flat RDG isosurfaces, in contrast to the bond path analysis, which is often bounded to a too localised and possibly discontinuous (yes/no) description. Conversely, the topological tool can provide quantitative insight into the simple, qualitative NCI picture offered by the RDG index. Hopefully, this study may pave the way to a deeper analysis of weak interactions in proteins using structural and ED information from experiment.
A novel descriptor for non‐covalent interactions, based on the reduced electron density gradient (RDG), enables easy visualisation of the zones of electron density ρ(r) involved in intermolecular interactions, for example, the CH⋅⋅⋅π interactions in the benzene crystal (see figure), whereas the quantum theory of atoms in molecules (QTAIM) bond path descriptor singles out two specific atom–atom links.
About 70 years ago, in the framework of his theory of chemical bonding, Pauling proposed an empirical correlation between the bond valences (or effective bond orders (BOs)) and the bond lengths. Till ...now, this simple correlation, basic in the bond valence model (BVM), is widely used in crystal chemistry, but it was considered irrelevant for metal-metal bonds. An extensive analysis of the quantum chemistry data computed in the last years confirms very well the validity of Pauling's correlation for both localized and delocalized interactions. This paper briefly summarizes advances in the application of the BVM for compounds with TM-TM bonds (TM = transition metal) and provides further convincing examples. In particular, the BVM model allows for very simple but precise calculations of the effective BOs of the TM-TM interactions. Based on the comparison between formal and effective BOs, we can easily describe steric and electrostatic effects. A possible influence of these effects on materials stability is discussed.
Boron is an element of fascinating chemical complexity. Controversies have shrouded this element since its discovery was announced in 1808: the new 'element' turned out to be a compound containing ...less than 60-70% of boron, and it was not until 1909 that 99% pure boron was obtained. And although we now know of at least 16 polymorphs, the stable phase of boron is not yet experimentally established even at ambient conditions. Boron's complexities arise from frustration: situated between metals and insulators in the periodic table, boron has only three valence electrons, which would favour metallicity, but they are sufficiently localized that insulating states emerge. However, this subtle balance between metallic and insulating states is easily shifted by pressure, temperature and impurities. Here we report the results of high-pressure experiments and ab initio evolutionary crystal structure predictions that explore the structural stability of boron under pressure and, strikingly, reveal a partially ionic high-pressure boron phase. This new phase is stable between 19 and 89 GPa, can be quenched to ambient conditions, and has a hitherto unknown structure (space group Pnnm, 28 atoms in the unit cell) consisting of icosahedral B12 clusters and B2 pairs in a NaCl-type arrangement. We find that the ionicity of the phase affects its electronic bandgap, infrared adsorption and dielectric constants, and that it arises from the different electronic properties of the B2 pairs and B12 clusters and the resultant charge transfer between them.
Most of TM6-cluster compounds (TM = transition metal) are soluble in polar solvents, in which the cluster units commonly remain intact, preserving the same atomic arrangement as in solids. ...Consequently, the redox potential is often used to characterize structural and electronic features of respective solids. Although a high lability and variety of ligands allow for tuning of redox potential and of the related spectroscopic properties in wide ranges, the mechanism of this tuning is still unclear. Crystal chemistry approach was applied for the first time to clarify this mechanism. It was shown that there are two factors affecting redox potential of a given metal couple: Lever’s electrochemical parameters of the ligands and the effective ionic charge of TM, which in cluster compounds differs effectively from the formal value due to the bond strains around TM atoms. Calculations of the effective ionic charge of TMs were performed in the framework of bond valence model, which relates the valence of a bond to its length by simple Pauling relationship. It was also shown that due to the bond strains the charge depends mainly on the atomic size of the inner ligands.
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