Theoretical description of alkali metal closo-boranes – towards the crystal structure of MgB12H12

Maniadaki, Aristea E.; Łodziana, Zbigniew

doi:10.1039/c8cp02371a

Cited by 8 publications

(12 citation statements)

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“…[11] For the 3D crystalline Mg(B 3 H 8 ) 2 , MgB 12 H 12 , and MgB 10 H 10 intermediates, the proposed structures calculated by Zhang et al were used. [3] In the case of 3D MgB 12 H 12 , we also tested the improved structural models proposed recently by Maniadaki et al [12] but the C2/m structure reported by Zhang et al [3] was found to have lower energy at the less refined level of theory adopted for our purposes. Nevertheless, it is important to emphasize that the energy variation among the 3D polymorphs (< 0.15 eV for Mg(BH 4 ) 2 and < 0.2 eV for MgB 12 H 12 ; see Figure S2 in the Supporting Information) was found to be smaller than the variation across dimensionalities, implying qualitative conclusions about morphology-dependent stability are relatively insensitive to the choice of 3D model crystal structure.…”

Section: Resultsmentioning

confidence: 99%

“…[3] In the case of MgB 12 H 12 , the proposed polymorphs from Ref. [12] were tested, and ultimately the C2/m structure was used because it had the lowest energy computed within PBE (rather than the more sophisticated van der Waals-corrected functionals used by the authors of Ref. [12]).…”

Section: Methodsmentioning

confidence: 99%

“…[12] were tested, and ultimately the C2/m structure was used because it had the lowest energy computed within PBE (rather than the more sophisticated van der Waals-corrected functionals used by the authors of Ref. [12]). For Mg(BH 4 ) 2 , the γ phase was found to be the most stable using PBE rather than the room-temperature α or high-temperature β phases.…”

Section: Methodsmentioning

confidence: 99%

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Morphology‐Dependent Stability of Complex Metal Hydrides and Their Intermediates Using First‐Principles Calculations

et al. 2019

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Complex light metal hydrides are promising candidates for efficient, compact solid-state hydrogen storage. (De)hydrogenation of these materials often proceeds via multiple reaction intermediates, the energetics of which determine reversibility and kinetics. At the solid-state reaction front, molecular-level chemistry eventually drives the formation of bulk product phases. Therefore, a better understanding of realistic (de)hydrogenation behavior requires considering possible reaction products along all stages of morphological evolution, from molecular to bulk crystalline. Here, we use first-principles calculations to explore the interplay between intermediate morphology and reaction pathways. Employing representative complex metal hydride systems, we investi-gate the relative energetics of three distinct morphological stages that can be expressed by intermediates during solidstate reactions: i) dispersed molecules; ii) clustered molecular chains; and iii) condensed-phase crystals. Our results verify that the effective reaction energy landscape strongly depends on the morphological features and associated chemical environment, offering a possible explanation for observed discrepancies between X-ray diffraction and nuclear magnetic resonance measurements. Our theoretical understanding also provides physical and chemical insight into phase nucleation kinetics upon (de)hydrogenation of complex metal hydrides.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Morphology‐Dependent Stability of Complex Metal Hydrides and Their Intermediates Using First‐Principles Calculations

et al. 2019

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“…The tg-Mn(B 12 H 12 ) is therefore a probable model for the long time searched structure of MgB 12 H 12 . Recent calculations predict MgB 12 H 12 .structure that is stabilized by the van der Waals attraction between aromatic closo-borane anions rather than covalent bond between the metal and B 12 H 12 [36].…”

Section: Discussionmentioning

confidence: 99%

Ethanol- and Methanol-Coordinated and Solvent-Free Dodecahydro closo-Dodecaborates of 3d Transition Metals and of Magnesium

et al. 2019

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Magnesium and 3d transition metals closo-borates were prepared by mechanosynthesis (ball milling) of the mixtures Na2B12H12 + MCl2 (M = Mn, Fe, Co, Ni, Mg), followed by addition of ethanol or methanol and drying under dynamic vacuum. The dead mass of NaCl is partly removed by filtration. The crystal structures of solvent-coordinated and solvent-free closo-borates have been characterized by temperature dependent synchrotron radiation X-ray powder diffraction, ab initio calculations, thermal analysis and infrared spectroscopy. Various solvated complexes containing six, four, three, two or one solvent molecules were obtained by successive removal of the solvent until in most case the solvent-free metal closo-borates were obtained with the exception of Mg whose hypothetical crystal structure, however, could have its prototype in MnB12H12. The 3d transition metal closo-borates were studied in the view of their potential use as Na- or Li-ion battery electrodes in combination with Na or Li closo-borate solid electrolytes. The metal oxidation state (II) obtained in compounds presented here does not allow such application.

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“…Contemporaneous with work done using borohydrides inside of solvents, borohydrides in the closo-borane phases were being considered as superionic conductors for rapid ion motion through their open channel pore structures [ 12 , 23 , 24 , 25 ]. Researchers doing theoretical work began to suggest that the superionic conduction would make closo-boranes promising for solid electrolytes [ 10 , 12 , 26 ]. The reasons for this superionic conduction are described in the theory paper by Kweon et al as a flat energy landscape (with many available sites for hopping), symmetry competition that ejects the cation from particular sites, and thermal reorientation of the anions [ 12 ].…”

Section: Borohydrides As Solid-state Electrolytesmentioning

confidence: 99%

Overview of the Structure–Dynamics–Function Relationships in Borohydrides for Use as Solid-State Electrolytes in Battery Applications

Dobbins

2021

Molecules

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The goal of this article is to highlight crucial breakthroughs in solid-state ionic conduction in borohydrides for battery applications. Borohydrides, Mz+BxHy, form in various molecular structures, for example, nido-M+BH4; closo-M2+B10H10; closo-M2+B12H12; and planar-M6+B6H6 with M = cations such as Li+, K+, Na+, Ca2+, and Mg2+, which can participate in ionic conduction. This overview article will fully explore the phase space of boron–hydrogen chemistry in order to discuss parameters that optimize these materials as solid electrolytes for battery applications. Key properties for effective solid-state electrolytes, including ionic conduction, electrochemical window, high energy density, and resistance to dendrite formation, are also discussed. Because of their open structures (for closo-boranes) leading to rapid ionic conduction, and their ability to undergo phase transition between low conductivity and high conductivity phases, borohydrides deserve a focused discussion and further experimental efforts. One challenge that remains is the low electrochemical stability of borohydrides. This overview article highlights current knowledge and additionally recommends a path towards further computational and experimental research efforts.

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Theoretical description of alkali metal closo-boranes – towards the crystal structure of MgB₁₂H₁₂

Abstract: Theoretical investigation of closo-boranes shows that dispersive interactions are important for such compounds. New structures of MgB12H12 are proposed.

Cited by 8 publications

References 67 publications

Morphology‐Dependent Stability of Complex Metal Hydrides and Their Intermediates Using First‐Principles Calculations

Morphology‐Dependent Stability of Complex Metal Hydrides and Their Intermediates Using First‐Principles Calculations

Ethanol- and Methanol-Coordinated and Solvent-Free Dodecahydro closo-Dodecaborates of 3d Transition Metals and of Magnesium

Overview of the Structure–Dynamics–Function Relationships in Borohydrides for Use as Solid-State Electrolytes in Battery Applications

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