Necessary and Sufficient Elastic Stability Conditions in Various Crystal Systems

While the Born elastic stability criteria are well-known for cubic crystals, there is some confusion in the literature about the form it should take for lower symmetry crystal classes. We present here closed form necessary and sufficient conditions for elastic stability in all crystal classes, as a concise and pedagogical reference to stability criteria in non-cubic materials

Computational characterization and prediction of metal-organic framework properties

In this introductory review, we give an overview of the computational chemistry methods commonly used in the field of metal-organic frameworks (MOFs), to describe or predict the structures themselves and characterize their various properties, either at the quantum chemical level or through classical molecular simulation. We discuss the methods for the prediction of crystal structures, geometrical properties and large-scale screening of hypothetical MOFs, as well as their thermal and mechanical properties. A separate section deals with the simulation of adsorption of fluids and fluid mixtures in MOFs

Responsive Metal–Organic Frameworks and Framework Materials: Under Pressure, Taking the Heat, in the Spotlight, with Friends

International audienceRecent years have seen a large increase of the research effort focused on framework materials, including the nowadays-ubiquitous metal−organic frameworks but also dense coordination polymers, covalent organic frameworks, and molecular frameworks. With the quickly increasing number of structures synthesized and characterized, one pattern emerging is the common occurrence of flexibility. More specifically, an important number of framework materials are stimuli-responsive: their structure can undergo changes of large amplitude in response to physical or chemical stimulation. They can display transformations induced by temperature, mechanical pressure, guest adsorption or evacuation, light absorption, etc. and are sometimes referred to as smart materials, sof t crystals, or dynamic materials. This Perspective highlights recent progress in this field, showcasing some of the most novel and unusual responses to stimuli, as well as advances in the fundamental understanding of flexible framework materials

Failure to Reproduce the Results of "A new transferable interatomic potential for molecular dynamics simulations of borosilicate glasses''

We reproduced the simulations described in Wang et al [J. Non-Cryst. Sol., 498 (2018) 294-304] and found we could not obtain the results reported. The root cause was identified to be incorrect atom masses in the original simulation files. As a consequence, the potential does not reproduce the experimental glass density -- and presumably, other structural properties -- and should be considered with great caution

Correcting the Scientific Record: Retraction Practices in Chemistry and Materials Science

International audienc

Novel Porous Polymorphs of Zinc Cyanide with Rich Thermal and Mechanical Behavior

We investigate the feasibility of four-connected nets as hypothetical zinc cyanide polymorphs, as well as their thermal and mechanical properties, through quantum chemical calculations and molecular dynamics simulations. We confirm the metastability of the two porous phases recently discovered experimentally (Lapidus, S. H.; et al. J. Am. Chem. Soc. 2013, 135, 7621-7628), suggest the existence of seven novel porous phases of Zn(CN)2, and show that isotropic negative thermal expansion is a common occurrence among all members of this family of materials, with thermal expansion coefficients close to that of the dense dia-c phase. In constrast, we find a wide variety in the mechanical behavior of these porous structures with framework-dependent anisotropic compressibilities. All porous structures, however, show pressure-induced softening leading to a structural transition at modest pressure.Comment: Chem. Mater. 201