The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Cameron J Kepert - One of the best experts on this subject based on the ideXlab platform.
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interpenetration as a mechanism for Negative Thermal Expansion in the metal organic framework cu3 btb 2 mof 14
Angewandte Chemie, 2014Co-Authors: Vanessa K Peterson, Emily Luks, Tamim A Darwish, Cameron J KepertAbstract:Metal–organic framework materials (MOFs) have recently been shown in some cases to exhibit strong Negative Thermal Expansion (NTE) behavior, while framework interpenetration has been found to reduce NTE in many materials. Using powder and single-crystal diffraction methods we investigate the Thermal Expansion behavior of interpenetrated Cu3(btb)2 (MOF-14) and find that it exhibits an anomalously large NTE effect. Temperature-dependent structural analysis shows that, contrary to other interpenetrated materials, in MOF-14 the large positive Thermal Expansion of weak interactions that hold the interpenetrating networks together results in a low-energy contractive distortion of the overall framework structure, demonstrating a new mechanism for NTE.
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elucidating Negative Thermal Expansion in mof 5
Journal of Physical Chemistry C, 2010Co-Authors: Nina Lock, Cameron J Kepert, Mogens Christensen, Lisa J Cameron, Vanessa K Peterson, Adam J Bridgeman, Bo B IversenAbstract:Multi-temperature X-ray diffraction studies show that twisting, rotation, and libration cause Negative Thermal Expansion (NTE) of the nanoporous metal−organic framework MOF-5, Zn4O(1,4-benzenedicarboxylate)3. The near-linear lattice contraction is quantified in the temperature range 80−500 K using synchrotron powder X-ray diffraction. Vibrational motions causing the abnormal Expansion behavior are evidenced by shortening of certain interatomic distances with increasing temperature according to single-crystal X-ray diffraction on a guest-free crystal over a broad temperature range. Detailed analysis of the atomic positional and displacement parameters suggests two contributions to cause the effect: (1) local twisting and vibrational motion of the carboxylate groups and (2) concerted transverse vibration of the linear linkers. The vibrational mechanism is confirmed by calculations of the dynamics in a molecular fragment of the framework.
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nanoporosity and exceptional Negative Thermal Expansion in single network cadmium cyanide
Angewandte Chemie, 2008Co-Authors: Anthony E Phillips, Andrew L Goodwin, Gregory J Halder, Peter D Southon, Cameron J KepertAbstract:Accentuate the Negative: Single-network cadmium cyanide displays isotropic Negative Thermal Expansion behavior of unprecedented magnitude over a large temperature range (see graph of unit cell parameter a versus temperature). Guest molecules in the pores of this framework block the transverse vibrational modes responsible for this behavior, causing the value of the linear coefficient of Thermal Expansion to increase with guest occupancy.
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compositional dependence of Negative Thermal Expansion in the prussian blue analogues miiptiv cn 6 m mn fe co ni cu zn cd
ChemInform, 2006Co-Authors: Karena W Chapman, Peter J Chupas, Cameron J KepertAbstract:The effect of MII substitution on the magnitude of the Negative Thermal Expansion (NTE) behavior within a series of Prussian Blue analogues, MIIPtIV(CN)6 for MII = Mn, Fe, Co, Ni, Cu, Zn, Cd, has b...
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guest dependent Negative Thermal Expansion in nanoporous prussian blue analogues miiptiv cn 6 x h2o 0 x 2 m zn cd
Journal of the American Chemical Society, 2005Co-Authors: Andrew L Goodwin, Karena W Chapman, Cameron J KepertAbstract:The guest-dependent Thermal Expansion behavior of the nanoporous Prussian Blue analogues MIIPtIV(CN)6.x{H2O} (0 Negative Thermal Expansion, attributed to Thermal population of low energy transverse vibrations of the bridging cyanide ligands. The presence of guest molecules within the framework pore system was found capable of dampening the effect of these transverse vibrational modes. The guest-loaded ZnII phase, in which the available pore volume is commensurate with the volume occupied by individual water molecules, possesses a considerably higher coefficient of Thermal Expansion, with the material switching from positive to Negative Thermal Expansion behavior upon guest removal.
Xianran Xing - One of the best experts on this subject based on the ideXlab platform.
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Negative Thermal Expansion in ybmn2ge2 induced by the dual effect of magnetism and valence transition
npj Quantum Materials, 2021Co-Authors: Yongqiang Qiao, Xianran Xing, Yuzhu Song, Longlong Fan, Hongjie Zhang, Qiang Sun, Andrea Sanson, Jun ChenAbstract:Negative Thermal Expansion (NTE) is an intriguing property, which is generally triggered by a single NTE mechanism. In this work, an enhanced NTE (αv = −32.9 × 10−6 K−1, ΔT = 175 K) is achieved in YbMn2Ge2 intermetallic compound to be caused by a dual effect of magnetism and valence transition. In YbMn2Ge2, the Mn sublattice that forms the antiferromagnetic structure induces the magnetovolume effect, which contributes to the NTE below the Neel temperature (525 K). Concomitantly, the valence state of Yb increases from 2.40 to 2.82 in the temperature range of 300–700 K, which simultaneously causes the contraction of the unit cell volume due to smaller volume of Yb3+ than that of Yb2+. As a result, such combined effect gives rise to an enhanced NTE. The present study not only sheds light on the peculiar NTE mechanism of YbMn2Ge2, but also indicates the dual effect as a possible promising method to produce enhanced NTE materials.
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magnetic field induced strong Negative Thermal Expansion in la fe al 13
Chemistry of Materials, 2020Co-Authors: Yuzhu Song, Qingzhen Huang, Rongjin Huang, Yun Liu, Zhenhuan Zhang, Yong Jiang, Shouguo Wang, Xianran XingAbstract:Negative Thermal Expansion (NTE) plays an increasingly important role in the control of Thermal Expansion of materials. However, the discovery of strong NTE materials, which is rare, remains challe...
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evidence of the enhanced Negative Thermal Expansion in 1 x pbtio3 xbi zn2 3ta1 3 o3
Inorganic chemistry frontiers, 2020Co-Authors: Tao Yang, Jun Chen, Jinxia Deng, Kun Lin, Yilin Wang, Na Wang, Xianran XingAbstract:A series of new solid solutions, (1 − x)PbTiO3-xBi(Zn2/3Ta1/3)O3 (0 < x < 0.2), have been synthesized, which show abnormally enhanced Negative Thermal Expansion. The results of synchrotron X-ray diffraction reveal that with the increase in the dopant of Bi(Zn2/3Ta1/3)O3 in the PbTiO3 system, the increase in spontaneous polarization displacement could improve the Negative Thermal Expansion behavior due to the spontaneous volume ferroelectrostriction (SVFS) effect. The STEM images show that PbTiO3-Bi(Zn2/3Ta1/3)O3 exhibits stronger polarization than PbTiO3, which reveals a greater deviation. Moreover, the STEM images show that the element Ta has larger spontaneous polarization displacement than other B-site atoms. Furthermore, density functional theory calculations confirm the enhancement of hybridization between the A-site cations and oxygen upon the introduction of Bi(Zn2/3Ta1/3)O3. All the above pieces of evidence indicate that the interplay between the cations and oxygen plays a key role in the enhancement of Negative Thermal Expansion.
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Negative Thermal Expansion in hf ti fe2 induced by the ferromagnetic and antiferromagnetic phase coexistence
Inorganic Chemistry, 2019Co-Authors: Yongqiang Qiao, Jun Chen, Jinxia Deng, Kun Lin, Yuzhu Song, Rongjin Huang, Yang Ren, Xinzhi Liu, Alexandra Franz, Xianran XingAbstract:Negative Thermal Expansion (NTE) is an intriguing physical phenomenon that can be used in the applications of Thermal Expansion adjustment of materials. In this study, we report a NTE compound of (Hf,Ti)Fe2, while both end members of HfFe2 and TiFe2 show positive Thermal Expansion. The results reveal that phase coexistence is detected in the whole NTE zone, in which one phase is ferromagnetic (FM), while the other is antiferromagnetic (AFM). With increasing temperature, the FM phase is gradually transformed to the AFM one. The NTE phenomenon occurs in the present (Hf,Ti)Fe2 because of the fact that the unit cell volume of the AFM phase is smaller than that of the FM phase, and the mass fraction of the AFM phase increases with increasing temperature. The construction of phase coexistence can be a method to achieve NTE materials in future studies.
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Negative Thermal Expansion in molecular materials
Chemical Communications, 2018Co-Authors: Zhanning Liu, Jun Chen, Jinxia Deng, Kun Lin, Qilong Gao, Xianran XingAbstract:Negative Thermal Expansion (NTE), whereby lattices contract upon heating, is of considerable interest for its wide applications in many fields. Molecular materials have been widely investigated as catalysts, sensors, etc., which usually endure temperature vibration. NTE can become a substantial means for controlling the coefficients of Thermal Expansion. Molecular materials possess plentiful structures and can be easily decorated, making them ideal platforms for Thermal Expansion modification. In this feature article, we provide an overview of the recent developments in utilizing NTE in molecular materials and summarize some mechanisms leading to NTE. The discussion of NTE in molecular materials concerns many factors, including transverse vibration, geometric flexibility, host-guest interactions, spin crossover, molecular packing rearrangement and molecular conformational changes.
Karena W Chapman - One of the best experts on this subject based on the ideXlab platform.
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pronounced Negative Thermal Expansion from a simple structure cubic scf3
Journal of the American Chemical Society, 2010Co-Authors: Benjamin K Greve, Kenneth L Martin, Peter L Lee, Peter J Chupas, Karena W Chapman, Angus P WilkinsonAbstract:Scandium trifluoride maintains a cubic ReO(3) type structure down to at least 10 K, although the pressure at which its cubic to rhombohedral phase transition occurs drops from >0.5 GPa at ∼300 K to 0.1-0.2 GPa at 50 K. At low temperatures it shows strong Negative Thermal Expansion (NTE) (60-110 K, α(l) ≈ -14 ppm K(-1)). On heating, its coefficient of Thermal Expansion (CTE) smoothly increases, leading to a room temperature CTE that is similar to that of ZrW(2)O(8) and positive Thermal Expansion above ∼1100 K. While the cubic ReO(3) structure type is often used as a simple illustration of how Negative Thermal Expansion can arise from the Thermally induced rocking of rigid structural units, ScF(3) is the first material with this structure to provide a clear experimental illustration of this mechanism for NTE.
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pressure enhancement of Negative Thermal Expansion behavior and induced framework softening in zinc cyanide
Journal of the American Chemical Society, 2007Co-Authors: Karena W Chapman, Peter J ChupasAbstract:The pressure-dependent structure and functionality of the coordination framework material zinc cyanide, Zn(CN)2, has been explored using in situ neutron powder diffraction. A third-order Birch−Murnaghan equation of state fit to variable pressure (0−0.6 GPa) data collected at ambient temperature (K0 = 34.19(21) GPa, K0‘ = −6.0(7)) shows that, contrary to behavior observed for typical materials, the Zn(CN)2 framework becomes more compressible at higher pressures. Variable temperature (50−300 K) data collected at 0.2 and 0.4 GPa indicate that the Negative Thermal Expansion effect in Zn(CN)2 becomes more pronounced at pressure with the coefficient of Thermal Expansion (α = dT/𝓁d𝓁) varying by ca. −1 × 10-6 K-1 per 0.2 GPa applied pressure up to an average (50−300 K) value of −19.42(23) × 10-6 K-1 at 0.4 GPa. Both these unusual phenomena have been linked to increased framework flexibility at high pressure.
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compositional dependence of Negative Thermal Expansion in the prussian blue analogues miiptiv cn 6 m mn fe co ni cu zn cd
ChemInform, 2006Co-Authors: Karena W Chapman, Peter J Chupas, Cameron J KepertAbstract:The effect of MII substitution on the magnitude of the Negative Thermal Expansion (NTE) behavior within a series of Prussian Blue analogues, MIIPtIV(CN)6 for MII = Mn, Fe, Co, Ni, Cu, Zn, Cd, has b...
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guest dependent Negative Thermal Expansion in nanoporous prussian blue analogues miiptiv cn 6 x h2o 0 x 2 m zn cd
Journal of the American Chemical Society, 2005Co-Authors: Andrew L Goodwin, Karena W Chapman, Cameron J KepertAbstract:The guest-dependent Thermal Expansion behavior of the nanoporous Prussian Blue analogues MIIPtIV(CN)6.x{H2O} (0 Negative Thermal Expansion, attributed to Thermal population of low energy transverse vibrations of the bridging cyanide ligands. The presence of guest molecules within the framework pore system was found capable of dampening the effect of these transverse vibrational modes. The guest-loaded ZnII phase, in which the available pore volume is commensurate with the volume occupied by individual water molecules, possesses a considerably higher coefficient of Thermal Expansion, with the material switching from positive to Negative Thermal Expansion behavior upon guest removal.
Andrew L Goodwin - One of the best experts on this subject based on the ideXlab platform.
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defect dependent colossal Negative Thermal Expansion in uio 66 hf metal organic framework
arXiv: Materials Science, 2015Co-Authors: Matthew J Cliffe, Claire A Murray, Joshua A Hill, Francoisxavier Coudert, Andrew L GoodwinAbstract:Thermally-densified hafnium terephthalate UiO-66(Hf) is shown to exhibit the strongest isotropic Negative Thermal Expansion (NTE) effect yet reported for a metal-organic framework (MOF). Incorporation of correlated vacancy defects within the framework affects both the extent of Thermal densification and the magnitude of NTE observed in the densified product. We thus demonstrate that defect inclusion can be used to tune systematically the physical behaviour of a MOF.
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geometric switching of linear to area Negative Thermal Expansion in uniaxial metal organic frameworks
CrystEngComm, 2014Co-Authors: Ines E Collings, Matthew G Tucker, David A Keen, Andrew L GoodwinAbstract:Using variable-temperature neutron powder diffraction measurements, we show that the two quartz-like metal–organic frameworks (MOFs) deuterium indium(III) terephthalate and zinc(II) isonicotinate exhibit anisotropic positive and Negative Thermal Expansion (PTE/NTE) behaviour. Whereas in the former the NTE response is uniaxial—occurring along the hexagonal crystal axis—this behaviour is inverted in the latter such that PTE occurs along the hexagonal axis and NTE is found in the entire plane of perpendicular directions. We show that this inversion of mechanical response can be explained on geometric grounds alone; specifically, we identify a critical framework geometry that demarcates a switch from linear to area NTE response. Extending this analysis to other common MOF topologies, we establish a generic predictive approach for establishing the dimensionality of NTE (or, by extension, Negative compressibility) responses in a large range of different framework systems. Our analysis suggests that framework geometry plays a crucial role in determining the mechanical response of framework materials which show anisotropic responses via hinging.
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nanoporosity and exceptional Negative Thermal Expansion in single network cadmium cyanide
Angewandte Chemie, 2008Co-Authors: Anthony E Phillips, Andrew L Goodwin, Gregory J Halder, Peter D Southon, Cameron J KepertAbstract:Accentuate the Negative: Single-network cadmium cyanide displays isotropic Negative Thermal Expansion behavior of unprecedented magnitude over a large temperature range (see graph of unit cell parameter a versus temperature). Guest molecules in the pores of this framework block the transverse vibrational modes responsible for this behavior, causing the value of the linear coefficient of Thermal Expansion to increase with guest occupancy.
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colossal positive and Negative Thermal Expansion in the framework material ag3 co cn 6
Science, 2008Co-Authors: Andrew L Goodwin, John S O Evans, Martin T Dove, M Calleja, Michael J Conterio, David A Keen, Lars Peters, Matthew G TuckerAbstract:We show that silver(I) hexacyanocobaltate(III), Ag3[Co(CN)6], exhibits positive and Negative Thermal Expansion an order of magnitude greater than that seen in other crystalline materials. This framework material expands along one set of directions at a rate comparable to the most weakly bound solids known. By flexing like lattice fencing, the framework couples this to a contraction along a perpendicular direction. This gives Negative Thermal Expansion that is 14 times larger than in ZrW2O8. Density functional theory calculations quantify both the low energy associated with this flexibility and the role of argentophilic (Ag+...Ag+) interactions. This study illustrates how the mechanical properties of a van der Waals solid might be engineered into a rigid, useable framework.
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Negative Thermal Expansion in zrw2o8 mechanisms rigid unit modes and neutron total scattering
Physical Review Letters, 2005Co-Authors: Matthew G Tucker, Andrew L Goodwin, Martin T Dove, David Keen, Stephen A Wells, John S O EvansAbstract:The local structure of the low-temperature ordered phase of the Negative Thermal Expansion (NTE) material ZrW2O8 has been investigated by reverse Monte Carlo (RMC) modeling of neutron total scattering data. We obtain, for the first time, quantitative measurements of the extent to which the WO4 and ZrO6 polyhedra move as rigid units, and we show that these values are consistent with the predictions of rigid unit mode theory. We suggest that rigid unit modes are associated with the NTE. Our results do not support a recent interpretation of x-ray-absorption fine structure spectroscopy data in terms of a larger rigid structural component involving the Zr-O-W linkage.
Jun Chen - One of the best experts on this subject based on the ideXlab platform.
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Negative Thermal Expansion in ybmn2ge2 induced by the dual effect of magnetism and valence transition
npj Quantum Materials, 2021Co-Authors: Yongqiang Qiao, Xianran Xing, Yuzhu Song, Longlong Fan, Hongjie Zhang, Qiang Sun, Andrea Sanson, Jun ChenAbstract:Negative Thermal Expansion (NTE) is an intriguing property, which is generally triggered by a single NTE mechanism. In this work, an enhanced NTE (αv = −32.9 × 10−6 K−1, ΔT = 175 K) is achieved in YbMn2Ge2 intermetallic compound to be caused by a dual effect of magnetism and valence transition. In YbMn2Ge2, the Mn sublattice that forms the antiferromagnetic structure induces the magnetovolume effect, which contributes to the NTE below the Neel temperature (525 K). Concomitantly, the valence state of Yb increases from 2.40 to 2.82 in the temperature range of 300–700 K, which simultaneously causes the contraction of the unit cell volume due to smaller volume of Yb3+ than that of Yb2+. As a result, such combined effect gives rise to an enhanced NTE. The present study not only sheds light on the peculiar NTE mechanism of YbMn2Ge2, but also indicates the dual effect as a possible promising method to produce enhanced NTE materials.
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role of dumbbell pairs of fe in spin alignments and Negative Thermal Expansion of lu2fe17 based intermetallic compounds
Inorganic Chemistry, 2020Co-Authors: Yili Cao, Jun Chen, Jinxia Deng, Kun Lin, Zhanning Liu, Chinwei Wang, E A Tereshinachitrova, Kenichi Kato, Hongjie ZhangAbstract:Knowledge of Negative Thermal Expansion (NTE) is an interesting issue in the field of materials science and engineering. It has been proposed that the unique dumbbell pairs of Fe (dumbbells) are hi...
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realizing isotropic Negative Thermal Expansion covering room temperature by breaking the superstructure of zrv2o7
Applied Physics Letters, 2020Co-Authors: Wei Wei, Jun Chen, Qilong Gao, Juan Guo, Mingju Chao, Erjun LiangAbstract:ZrV2O7 is a well-known isotropic Negative Thermal Expansion (NTE) material. However, the NTE property of ZrV2O7 can only be observed in high temperatures above 375 K. In this paper, we report a facile method to break the superstructure of ZrV2O7 for realizing the NTE property of ZrV2O7 to room temperature by partial substitution of Mo for V atoms. The detailed structure information and the phase transition process are revealed by high-resolution synchrotron x-ray diffraction, neutron powder diffraction, and high pressure Raman spectral analyses. It is found that the incorporation of Mo prompts the V-O2-V/Mo angles to expand from 160° to 180°, which enables the NTE property at room temperature. Different from most open framework structures where NTE is dominated by low energy phonons, here several high energy phonon modes are found to have Negative Gruneisen parameters and contribute to the Negative Thermal Expansion.
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realizing isotropic Negative Thermal Expansion covering room temperature by breaking the superstructure of zrv 2 o 7
Applied Physics Letters, 2020Co-Authors: Wei Wei, Jun Chen, Qilong Gao, Juan Guo, Mingju Chao, Erjun LiangAbstract:ZrV2O7 is a well-known isotropic Negative Thermal Expansion (NTE) material. However, the NTE property of ZrV2O7 can only be observed in high temperatures above 375 K. In this paper, we report a facile method to break the superstructure of ZrV2O7 for realizing the NTE property of ZrV2O7 to room temperature by partial substitution of Mo for V atoms. The detailed structure information and the phase transition process are revealed by high-resolution synchrotron x-ray diffraction, neutron powder diffraction, and high pressure Raman spectral analyses. It is found that the incorporation of Mo prompts the V-O2-V/Mo angles to expand from 160° to 180°, which enables the NTE property at room temperature. Different from most open framework structures where NTE is dominated by low energy phonons, here several high energy phonon modes are found to have Negative Gruneisen parameters and contribute to the Negative Thermal Expansion.
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evidence of the enhanced Negative Thermal Expansion in 1 x pbtio3 xbi zn2 3ta1 3 o3
Inorganic chemistry frontiers, 2020Co-Authors: Tao Yang, Jun Chen, Jinxia Deng, Kun Lin, Yilin Wang, Na Wang, Xianran XingAbstract:A series of new solid solutions, (1 − x)PbTiO3-xBi(Zn2/3Ta1/3)O3 (0 < x < 0.2), have been synthesized, which show abnormally enhanced Negative Thermal Expansion. The results of synchrotron X-ray diffraction reveal that with the increase in the dopant of Bi(Zn2/3Ta1/3)O3 in the PbTiO3 system, the increase in spontaneous polarization displacement could improve the Negative Thermal Expansion behavior due to the spontaneous volume ferroelectrostriction (SVFS) effect. The STEM images show that PbTiO3-Bi(Zn2/3Ta1/3)O3 exhibits stronger polarization than PbTiO3, which reveals a greater deviation. Moreover, the STEM images show that the element Ta has larger spontaneous polarization displacement than other B-site atoms. Furthermore, density functional theory calculations confirm the enhancement of hybridization between the A-site cations and oxygen upon the introduction of Bi(Zn2/3Ta1/3)O3. All the above pieces of evidence indicate that the interplay between the cations and oxygen plays a key role in the enhancement of Negative Thermal Expansion.
