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Large negative thermal expansion in GdFe(CN)_(6) driven by unusual low-frequency modes

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Chinese Chemical Letters 2023年第5期34卷 557-560页

作者： Qilong Gao Yixin Jiao andrea sanson Erjun Liang Qiang Sun Key Laboratory of Materials Physics of Ministry of Education and School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China Department of Physics and Astronomy University of PadovaPadova I-35131Italy

Understanding the negative thermal expansion(NTE)mechanism is of great *** this work,we consider the new NTE compound Gd Fe(CN)_(6)(α_(v)=-34.2×10^(-6)K^(-1))as a case study to investigate the NTE mechanism from the perspective of the lattice vibrational *** atomic mean-square displacements suggest that the NTE of Gd Fe(CN)_(6)comes from the strong tension effect induced by the transverse vibrations of the atomic-Fe-C≡N-Gd-linkages,with the largest contribution given by N *** dynamics calculations show that three low-frequency optical modes at about 50 cm^(-1)show the largest negative Grüneisen parameters thus providing the largest contribution to the *** existence of these unusual low-frequency vibrational modes can be ascribed to the presence of GdN_(6)trigonal prisms in the framework structure of Gd Fe(CN)_(6).

关键词： Negative thermal expansion Prussian blue analogues Low frequency phonon Crystal structure Transverse vibration

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Zn(NCN)单轴的负热膨胀性及机理研究

高等学校化学学报 2022年第6期43卷 160-165页

作者：施耐克张娅 sanson andrea 王蕾陈骏北京科技大学物理化学系北京材料基因工程高精尖创新中心北京100083 意大利帕多瓦大学天文物理系帕多瓦I-35131 北京科技大学物理系北京100083

负热膨胀(NTE)是一种反常的物理现象,已在合金和框架结构化合物等材料中被观察到,但NTE材料的种类仍然有限.本文合成了一种单轴NTE材料Zn(NCN),该材料在c轴方向及在100~475 K下的热膨胀系数为−3.35×10^(‒6)K^(‒1),而a轴和b轴方向则呈... 详细信息

负热膨胀(NTE)是一种反常的物理现象,已在合金和框架结构化合物等材料中被观察到,但NTE材料的种类仍然有限.本文合成了一种单轴NTE材料Zn(NCN),该材料在c轴方向及在100~475 K下的热膨胀系数为−3.35×10^(‒6)K^(‒1),而a轴和b轴方向则呈低热膨胀性,体积具有低的热膨胀系数[6.13×10^(‒6)K^(‒1)(100~475 K)].通过同步辐射X射线衍射、扩展X射线吸收精细结构和拉曼光谱等方法,研究了Zn(NCN)的NTE机理.结果表明,Zn—N键具有明显的横向振动,一些低频振动模Grüneisen参数为负值.直接的实验证据表明,N=C=N的横向振动以及准刚性ZnN4四面体的耦合旋转和扭摆导致了c轴方向的NTE.

关键词：负热膨胀框架结构晶体结构氰胺锌横向振动

A new isotropic negative thermal expansion material of CaSnF_(6)with facile and low-cost synthesis

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Nano Research 2023年第4期16卷 5964-5972页

作者： Qilong Gao Sen Zhang Yixin Jiao Yongqiang Qiao andrea sanson Qiang Sun Xinwei Shi Erjun Liang Jun Chen Key Laboratory of Materials Physics of Ministry of Education and School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China Department of Physics and Astronomy University of PadovaPadova I-35131Italy Beijing Advanced Innovation Center for Materials Genome Engineering Department of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China

Double ReO_(3)-type fluorides have a great interest in the field of negative thermal expansion(NTE)and luminescent ***,their application is limited by the scarcity of quantity,expensive raw materials,and harsh preparation *** this work we have found a new NTE material,CaSnF_(6),by applying the concept of the average atomic *** importantly,different from the previous solid-phase sintering and direct fluorination methods,the nano CaSnF6 has been synthesized for the first time by solvothermal *** results of X-ray diffraction(XRD)and Raman spectroscopy show that a phase transition occurs from rhombohedral(R3)to cubic(Fm3m)structure at about 200 K,and a strong isotropic NTE(αv=−15.78×10^(−6)K^(−1))appears in the cubic *** dynamics calculations from first-principles illustrate that the NTE is due to the transverse vibration of fluorine atoms excited by low-frequency *** work not only broadens the NTE family of fluorides,but also provides a new facile and low-cost fabricati on method for the preparation of NTE fluorides.

关键词： negative thermal expansion double ReO_(3)-type fluorides Grüneisen parameters lattice dynamics

Simple chemical synthesis and isotropic negative thermal expansion in MHfF_(6)(M=Ca,Mn,Fe,and Co)

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Nano Research 2024年第3期17卷 2195-2203页

作者： Yongqiang Qiao Sen Zhang Peixian Zhang Juan Guo andrea sanson Xi Zhen Kaiyue Zhao Qilong Gao Jun Chen Key Laboratory of Materials Physics of Ministry of Education and School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China Department of Physics and Astronomy University of PadovaPadova I-35131Italy Beijing Advanced Innovation Center for Materials Genome Engineering Department of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China

The rapid progress of modern technologies has accelerated the prominence of thermal expansion mismatch between materials,and tunable thermal expansion materials will be a powerful safeguard against this ***,isotropic MHfF_(6)(M=Ca,Mn,Fe,and Co)compounds with tunable thermal expansion have been produced via a low-cost synthetic method and *** utilizing temperature dependent X-ray diffraction(XRD)and Raman spectroscopy,combined with first principles calculations,it was revealed that the transverse thermal vibrations of the F atoms are dominated by low-frequency phonons with negative Grüneisen parameters and are therefore the origin of the negative thermal expansion(NTE).Very interestingly,with the increase of the M atomic number,the metal…F atomic linkages become stiffer,reducing the number of vibrational modes with negative Grüneisen parameters,so that the strong NTE can be gradually adjusted to moderate NTE and to near zero thermal *** present study achieves the tunable thermal expansion in a new compound family and shed light on the internal mechanism from the perspective of lattice vibrational dynamics.

关键词： negative thermal expansion fluorides chemical synthesis nanosheet structure first principles calculations

The role of average atomic volume in predicting negative thermal expansion:The case of REFe(CN)_(6)

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Science China Materials 2022年第2期65卷 553-557页

作者： Qilong Gao Qiang Sun Alessandro Venier andrea sanson Qingzhen Huang Yu Jia Erjun liang Jun Chen Key Laboratory of Materials Physics of Ministry of Education and School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China Beijing Advanced Innovation Center for Materials Genome Engineering School of Mathematics and PhysicsDepartment of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China Department of Physics and Astronomy University of PadovaPadova I-35131Italy NIST Center for Neutron Research National Institute of Standards and TechnologyGaithersburg MD20899-6102United States Key Laboratory of Special Functional Materials of Ministry of Education of China and School of Materials Science and EngineeringHenan UniversityKaifeng 475004China

Negative thermal expansion(NTE),as an abnormal physical behavior,has been followed by scientists’attention over the past 30 years,due to its fascinating physical mechanisms and the prospect of high-precision thermal expansion control[1-5].Although some NTE materials(alloys[6],cyanides[7],fluorides[8-10],nitrides[11],oxides[12,13],MOFs[14-16],etc.)have been found,their number and variety are still very small,limiting their *** and designing new NTE materials is an important and challenging topic for the development of the field of *** have been continually reviewing and summarizing obtained results to look to the future of NTE[17-23].

关键词：原子晶格负热膨胀第一性原理计算热振动振动模式低频声定性预测