Low-temperature crystal structure, specific heat, and dielectric properties of lithium tetraborate Li2B4O7

Senyshyn, Anatoliy; Schwarz, Björn; Lorenz, T.; Адамів, В.Т.; Bürak, Ya. I.; Banys, J.; Grigalaitis, R.; Vasylechko, L.; Ehrenberg, Helmut; Fueß, H.

doi:10.1063/1.3504244

Cited by 32 publications

(9 citation statements)

References 50 publications

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“…16 NTE has been observed via x-ray powder diffraction 17 and coherent neutron powder diffraction experiments in Li 2 B 4 O 7 . 18,19 The expansion in this material is anisotropic, with the contraction of one lattice parameter dominating the low-temperature volume dependence. The Li ions show strong T dependence of their meansquared displacements around 100 K, temperature at which NTE vanishes in the material.…”

Section: Introductionmentioning

confidence: 99%

Classical model of negative thermal expansion in solids with expanding bonds

Schick

Rappe

2016

Phys. Rev. B

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We study negative thermal expansion (NTE) in model lattices with multiple atoms per cell and first-and second-nearest neighbor interactions using the (anharmonic) Morse potential. By exploring the phase space of neighbor distances and thermal expansion rates of the bonds, we determine the conditions under which NTE emerges. By permitting all bond lengths to expand at different rates, we find that NTE is possible without appealing to fully rigid units. Nearly constant, large-amplitude, isotropic NTE is observed up to the melting temperature in a classical molecular dynamics model of a ReO 3 -like structure when the rigidity of octahedral units is almost completely eliminated. Only weak NTE, changing over to positive expansion is observed when the corner-linked octahedra are rigid, with flexible second-neighbor bonds between neighboring octahedra permitting easy rotation. We observe similar changes to thermal expansion behavior for the diamond lattice: NTE when second-neighbor interactions are weak to positive thermal expansion when second-neighbor interactions are strong. From these observations, we suggest that the only essential local conditions for NTE are atoms with low coordination numbers along with very low energies for changing bond angles relative to bond-stretching energies. 65.40.De

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Section: Introductionmentioning

confidence: 99%

Classical model of negative thermal expansion in solids with expanding bonds

Schick

Rappe

2016

Phys. Rev. B

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“…The thermal invariability of rigid groups has been proven by single crystal HTXRD and LTXRD studies (HT, high temperature; LT low temperature) of about a dozen of borates [46][47][48][49][50][51][52][53][54][55][56][57][58], etc. These results have been summarized in [26,34,42,43] and are briefly described here.…”

Section: Thermal Invariability Of Rigid B-o Groupsmentioning

confidence: 99%

Borates—Crystal Structures of Prospective Nonlinear Optical Materials: High Anisotropy of the Thermal Expansion Caused by Anharmonic Atomic Vibrations

et al. 2017

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Abstract:In the present study the thermal structure evolution is reviewed for known nonlinear optical borates such as β- (98-348 K). In addition to the established criteria for nonlinear optical (NLO) properties of crystals, here the role of the anisotropy and anharmonicity of the thermal vibrations of atoms is analysed as well as changes in their coordination spheres and the anisotropy of the thermal expansion of the crystal structure. Non-centrosymmetric borates, especially those that have NLO properties, often show distinct anisotropies for each cation in comparison to centrosymmetric borates. All considered NLO borates contain BO 3 triangles, which are the principal cause of the strong anisotropy of the thermal expansion.Keywords: NLO borates; crystal structures at low and high temperatures; rigid boron-oxygen groups; anisotropic and anharmonic atomic vibrations; thermal expansion; low-and high-temperature single-crystal and powder X-ray diffraction

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“…Pioneering works by Wojciechowski et al showed negative compressibility in thin layers of microscopic systems, while Chen et al in the early 1980s result in polymeric NTE materials. In its short span of history, NTE solids have been developed from all classes of materials . Greater flexibility for application can be found in the case of adjustable CTEs by means of connected triangular blocks , multilayed system and sharp particle (needle‐like) reinforced composites .…”

Section: Motivationmentioning

confidence: 99%

Negative thermal expansion in transversely isotropic space frame trusses

Lim

2013

Physica Status Solidi (b)

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The negative thermal expansion (NTE) of a type of space frame structure is investigated herein. On the basis of a space frame structure consisting of tetrahedral representative volume elements, a volumetric thermal strain and a volumetric coefficient of thermal expansion (CTE) models are developed in this paper. The NTE trusses developed herein exhibit a special case of anisotropy known as transverse isotropy. This is achieved by using two types of rod materials, each for the three apex rods and the three base rods. From these models, the conditions for attaining negative volumetric strain and negative coefficients of volumetric expansion due to change in temperature are established. Two definitions of NTE are given herein: (a) overall NTE and (b) incremental NTE. Based on these two definitions of NTE, the conditions that lead to (i) definite NTE and (ii) selective NTE are established. Plotted results reveal a trend in which the extent of negative thermal expansion is increased for lower apex‐to‐base rod length and CTE ratios, and higher base rod CTE.

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Low-temperature crystal structure, specific heat, and dielectric properties of lithium tetraborate Li2B4O7

Cited by 32 publications

References 50 publications

Classical model of negative thermal expansion in solids with expanding bonds

Classical model of negative thermal expansion in solids with expanding bonds

Borates—Crystal Structures of Prospective Nonlinear Optical Materials: High Anisotropy of the Thermal Expansion Caused by Anharmonic Atomic Vibrations

Negative thermal expansion in transversely isotropic space frame trusses

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