DEM investigation on strain localization in a dense periodic granular assembly with high coordination number

Strain localization is one of key phenomena which have been studied extensively in geomaterials and for different kinds of materials including metals and polymers. This well-known phenomenon appears when structure/material is closed to failure. Theoretical, experimental, and numerical research have been dedicated to this subject for a long while. In the numerical aspects, strain localization inside the periodic granular assembly has not been well studied in the literature. In this paper, we investigate the occurrence and development of strain localization within a dense cohesive-frictional granular assembly with high coordination number under bi-periodic boundary conditions by Discrete Element Modeling (DEM). The granular assembly is composed of 2D circular disks and subjected to biaxial loading with constant lateral pressure. The results show that the formation of shear bands is of periodic type, consistent with the boundary conditions. This formation has the origins of the irreversible losing of cohesive contacts, viewed as micro-crackings which strongly concentrated in the periodic shear zones. This micromechanical feature is therefore strongly related to the strain localization observed at the sample scale. Finally, we also show that the strain localization is in perfect agreement with the sample’s displacement fluctuation fields.

Theoretical probing of twenty-coordinate actinide-centered boron molecular drums

The exploration of metal-doped boron clusters has a great significance to design high coordination number (CN) compounds. Actinide-dopted boron clusters are probably candidates for achieving high CNs. In this work,...

High coordination number actinide-noble gas complexes; a computational study

Computational quantum chemical techniques are used to explore charged actinide-noble gas compounds, including new Th–He systems with record coordination number.

High-Coordinate Mononuclear Ln(III) Complexes: Synthetic Strategies and Magnetic Properties

Single-molecule magnets involving monometallic 4f complexes have been investigated extensively in last two decades to understand the factors that govern the slow magnetization relaxation behavior in these complexes and to establish a magneto-structural correlation. The prime goal in this direction is to suppress the temperature independent quantum tunneling of magnetization (QTM) effect via fine-tuning the coordination geometry/microenvironment. Among the various coordination geometries that have been pursued, complexes containing high coordination number around Ln(III) are sparse. Herein, we present a summary of the various synthetic strategies that were used for the assembly of 10- and 12-coordinated Ln(III) complexes. The magnetic properties of such complexes are also described.

New theoretical insight into high coordination number complexes in actinides-centered borane

<p>The coordination number of a given element behaving to understand its chemistry shows a great interest, which greatly promotes the extension and development of new materials, but remains challenging. Herein we report a new record high coordination number (CN) for actinide established in the cage-like An(BH)₂₄ (An = Th to Cm) via using relativistic quantum chemistry methods. Analysis of U(BH)_n (n = 1 to 24) confirms these series of systems being as geometric minima, with the BH as a ligand located in the first shell around the uranium. Contrast, global searches reveal the low CN half-cage structure for UB₂₄, which is extended to the series of AnB₂₄ and prevails over the competing structural isomers such as cage. The intrinsic geometric difference for AnB₂₄and An(BH)₂₄ mainly arise from the B sp³ hybridization in borane inducing strong interactions between An 5f6d7s hybrid orbitals and B 2p_z orbitals in An(BH)₂₄ comparing to that of AnB₂₄. The fundamental trend presents a valuable insight for future experimental endeavor searching for isolable complexes with high-coordination actinide and provides a new structural motif of boron clusters and nanostructures.<br></p>

New theoretical insight into high coordination number complexes in actinides-centered borane

<p>The coordination number of a given element behaving to understand its chemistry shows a great interest, which greatly promotes the extension and development of new materials, but remains challenging. Herein we report a new record high coordination number (CN) for actinide established in the cage-like An(BH)₂₄ (An = Th to Cm) via using relativistic quantum chemistry methods. Analysis of U(BH)_n (n = 1 to 24) confirms these series of systems being as geometric minima, with the BH as a ligand located in the first shell around the uranium. Contrast, global searches reveal the low CN half-cage structure for UB₂₄, which is extended to the series of AnB₂₄ and prevails over the competing structural isomers such as cage. The intrinsic geometric difference for AnB₂₄and An(BH)₂₄ mainly arise from the B sp³ hybridization in borane inducing strong interactions between An 5f6d7s hybrid orbitals and B 2p_z orbitals in An(BH)₂₄ comparing to that of AnB₂₄. The fundamental trend presents a valuable insight for future experimental endeavor searching for isolable complexes with high-coordination actinide and provides a new structural motif of boron clusters and nanostructures.<br></p>

New theoretical insights into high-coordination-number complexes in actinides-centered borane

The coordination number of a given element affects its behavior, and consequently, there is great interest in understanding the related chemistry, which could greatly promote the extension and development of new materials, but remains challenging.

Air-Stable Hexagonal Bipyramidal Dysprosium(III) Single-Ion Magnets with Nearly Perfect D6h Local Symmetry

Local eight-coordination of the Dy(III) with D_6h symmetry receives much expectation for high-performance single-molecule magnets (SMMs) due to the simultaneous fulfillment of the magnetic axiality and high coordination number (a requisite for the air stability). But the experimental realization is challenging due to the required restriction of six coordination atoms in the equatorial plane of the hexagonal-bipyramid, which is usually too crowded for the central Dy(III) ion. Here we show by using the hexaaza macrocyclic Schiff base ligand and fine-tuning the axial alkoxide/phenol type ligands, a family of hexagonal-bipyramidal Dy(III) complexes, namely [Dy^III(L)(Cl)₂(H₂O/CH₃OH)]Cl <b>1</b>, [Dy^III(L)(C₆F₅O)₂(H₂O)](BPh₄)·<b>2</b>, [Dy^III(L)(PhO)₂](BPh₄) <b>3</b>, [Dy^III(L)(4-MeO-PhO)₂](BPh₄) <b>4</b>, [Dy^III(L)(naPhO)₂](BPh₄) <b>5 </b>and [Dy^III(L)(Ph₃SiO)₂](BPh₄) <b>6</b><b> </b>, can be isolated. Among them, complexes <b>3</b>, <b>4</b> and <b>5</b> possess nearly perfect D_6h local symmetry. Complex <b>4</b> shows the highest effective magnetic reversal barrier 1338 K and an open hysteresis temperature 6 K at the field sweeping rate of 1.2 mT/s, which represents a new record for D_6h SMMs.

Air-Stable Hexagonal Bipyramidal Dysprosium(III) Single-Ion Magnets with Nearly Perfect D6h Local Symmetry

Local eight-coordination of the Dy(III) with D_6h symmetry receives much expectation for high-performance single-molecule magnets (SMMs) due to the simultaneous fulfillment of the magnetic axiality and high coordination number (a requisite for the air stability). But the experimental realization is challenging due to the required restriction of six coordination atoms in the equatorial plane of the hexagonal-bipyramid, which is usually too crowded for the central Dy(III) ion. Here we show by using the hexaaza macrocyclic Schiff base ligand and fine-tuning the axial alkoxide/phenol type ligands, a family of hexagonal-bipyramidal Dy(III) complexes, namely [Dy^III(L)(Cl)₂(H₂O/CH₃OH)]Cl <b>1</b>, [Dy^III(L)(C₆F₅O)₂(H₂O)](BPh₄)·<b>2</b>, [Dy^III(L)(PhO)₂](BPh₄) <b>3</b>, [Dy^III(L)(4-MeO-PhO)₂](BPh₄) <b>4</b>, [Dy^III(L)(naPhO)₂](BPh₄) <b>5 </b>and [Dy^III(L)(Ph₃SiO)₂](BPh₄) <b>6</b><b> </b>, can be isolated. Among them, complexes <b>3</b>, <b>4</b> and <b>5</b> possess nearly perfect D_6h local symmetry. Complex <b>4</b> shows the highest effective magnetic reversal barrier 1338 K and an open hysteresis temperature 6 K at the field sweeping rate of 1.2 mT/s, which represents a new record for D_6h SMMs.