Complexity in surfaces of densest packings for families of polyhedra

Packings of hard polyhedra have been studied for centuries due to their mathematical aesthetic and more recently for their applications in fields such as nanoscience, granular and colloidal matter, and biology. In all these fields, particle shape is important for structure and properties, especially upon crowding. Here, we explore packing as a function of shape. By combining simulations and analytic calculations, we study three 2-parameter families of hard polyhedra and report an extensive and systematic analysis of the densest packings of more than 55,000 convex shapes. The three families have the symmetries of triangle groups (icosahedral, octahedral, tetrahedral) and interpolate between various symmetric solids (Platonic, Archimedean, Catalan). We find that optimal (maximum) packing density surfaces that reveal unexpected richness and complexity, containing as many as 130 different structures within a single family. Our results demonstrate the utility of thinking of shape not as a static property of an object in the context of packings, but rather as but one point in a higher dimensional shape space whose neighbors in that space may have identical or markedly different packings. Finally, we present and interpret our packing results in a consistent and generally applicable way by proposing a method to distinguish regions of packings and classify types of transitions between them.Comment: 16 pages, 8 figure

Role of short-range order and hyperuniformity in the formation of band gaps in disordered photonic materials

We study photonic band gap formation in two-dimensional high-refractive-index disordered materials where the dielectric structure is derived from packing disks in real and reciprocal space. Numerical calculations of the photonic density of states demonstrate the presence of a band gap for all polarizations in both cases. We find that the band gap width is controlled by the increase in positional correlation inducing short-range order and hyperuniformity concurrently. Our findings suggest that the optimization of short-range order, in particular the tailoring of Bragg scattering at the isotropic Brillouin zone, are of key importance for designing disordered PBG materials

A Directional Entropic Force Approach to Assemble Anisotropic Nanoparticles into Superlattices

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102143/1/14230_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102143/2/ange_201306009_sm_miscellaneous_information.pd

Crystalline Assemblies and Densest Packings of a Family of Truncated Tetrahedra and the Role of Directional Entropic Forces

Polyhedra and their arrangements have intrigued humankind since the ancient Greeks and are today important motifs in condensed matter, with application to many classes of liquids and solids. Yet, little is known about the thermodynamically stable phases of polyhedrally-shaped building blocks, such as faceted nanoparticles and colloids. Although hard particles are known to organize due to entropy alone, and some unusual phases are reported in the literature, the role of entropic forces in connection with polyhedral shape is not well understood. Here, we study thermodynamic self-assembly of a family of truncated tetrahedra and report several atomic crystal isostructures, including diamond, {\beta}-tin, and high- pressure lithium, as the polyhedron shape varies from tetrahedral to octahedral. We compare our findings with the densest packings of the truncated tetrahedron family obtained by numerical compression and report a new space filling polyhedron, which has been overlooked in previous searches. Interestingly, the self-assembled structures differ from the densest packings. We show that the self-assembled crystal structures can be understood as a tendency for polyhedra to maximize face-to-face alignment, which can be generalized as directional entropic forces.Comment: Article + supplementary information. 23 pages, 10 figures, 2 table

Management policies for invasive alien species: Adressing the impacts rather than the species

Effective long-term management is needed to address the impacts of invasive alien species (IAS) that cannot be eradicated. We describe the fundamental characteristics of long-term management policies for IAS, diagnose a major shortcoming, and outline how to produce effective IAS management. Key international and transnational management policies conflate addressing IAS impacts with controlling IAS populations. This serious purpose–implementation gap can preclude the development of broader portfolios of interventions to tackle IAS impacts. We posit that IAS management strategies should directly address impacts via impact-based interventions, and we propose six criteria to inform the choice of these interventions. We review examples of interventions focused on tackling IAS impacts, including IAS control, which reveal the range of interventions available and their varying effectiveness in counteracting IAS impacts. As the impacts caused by IAS increase globally, stakeholders need to have access to a broader and more effective set of tools to respond.Fil: García Díaz, Pablo. University of Aberdeen; Reino UnidoFil: Cassey, Philip. University of Adelaide; AustraliaFil: Norbury, Grant. Crown Research Institutes. Landcare Research; Nueva ZelandaFil: Lambin, Xavier. University of Aberdeen; Reino UnidoFil: Montti, Lia Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Pizarro, J. Cristóbal. Universidad de Concepción; ChileFil: Powell, Priscila Ana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Burslem, David F. R. P.. University of Aberdeen; Reino UnidoFil: Cava, Mário. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Damasceno, Gabriella. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Fasola, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Asociación Ornitológica del Plata; ArgentinaFil: Fidelis, Alessandra. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Huerta, Magdalena F.. Universidad Austral de Chile; Chile. Universidad de Concepción; ChileFil: Langdon, Bárbara. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma | Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma.; ArgentinaFil: Linardaki, Eirini. University of Aberdeen; Reino UnidoFil: Moyano, Jaime. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma | Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma.; ArgentinaFil: Nuñez, Martin Andres. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma | Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma.; ArgentinaFil: Pauchard, Aníbal. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma | Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Instituto de Investigaciones En Biodiversidad y Medioambiente. Subsede San Martín de Los Andes-inibioma.; ArgentinaFil: Phimister, Euan. University of Aberdeen; Reino UnidoFil: Raffo, Eduardo. Gobierno de Chile. Servicio Agrícola y Ganadero; ChileFil: Roesler, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Rodríguez Jorquera, Ignacio. Universidad Austral de Chile; Chile. Universidad de Concepción; ChileFil: Tomasevic, Jorge A.. Universidad Austral de Chile; Chile. Universidad de Concepción; Chil

Identifying priorities, targets, and actions for the long-term social and ecological management of invasive non-native species

Funding: The research and the workshop (December-2019; Centro Científico Tecnológico Patagonia Norte, San Carlos de Bariloche, Argentina) described in this manuscript were funded by the CONTAIN programme under the Latin American Biodiversity Programme as part of the Newton Fund (NE/S011641/1), with contributions from NERC, the Argentine National Scientific & Technical Research Council (CONICET,-2019-74-APN-DIR#CONICET), the Brazilian São Paulo Research Foundation (FAPESP 2018/14995-8), and the Chilean Agency for Research and Development (ANID; formerly CONICYT). Acknowledgments Thanks to the colleagues who replied to our informal questions about the usefulness of the methods and procedures described here. This informal survey of colleagues to obtain an initial critical evaluation was aligned with the policies relevant to the authors who contacted the participants. No one else had access to the responses and identities of the respondents. Servicio Agrícola y Ganadero, Gobierno de Chile, is one of the CONTAIN project partners, and it is represented by ER in this paper. However, the opinions and results presented in this document are entirely those of ER and may not represent SAG position on the topic. The Associate Editor and two reviewers provided feedback that helped improve a previous version of the manuscript. Open access via Springer compact agreementPeer reviewedPublisher PD