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First-principles calculations of elasticity of minerals at high temperature and pressure

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Science China Earth Sciences 2016年第6期59卷 1107-1137页

作者： wu zhongqing WANG WenZhong Laboratory of Seismology and Physics of Earth's Interior School of Earth and Space ScienceUniversity of Science and Technology of ChinaHefei 230026China Mengcheng National Geophysical Observatory Mengcheng 233527China

The elasticity of minerals at high temperature and pressure （PT） is critical for constraining the composition and temperature of the Earth＇s interior and understand better the deep water cycle and the dynamic Earth. First-principles calcula- tions without introducing any adjustable parameters, whose results can be comparable to experimental data, play a more and more important role in investigating the elasticity of minerals at high PT mainly because of （1） the quick increasing of computational powers and （2） advances in method. For example, the new method reduces the computation loads to one-tenth of the traditional method with the comparable precise as the traditional method. This is extraordinarily helpful because first-principles calculations of the elasticity of minerals at high PT are extremely time-consuming. So far the elasticity of most of lower mantle minerals has been investigated in detail. We have good idea on the effect of temperature, pressure, and iron concentration on elasticity of main minerals of the lower mantle and the unusual softening in bulk modulus by the spin crosso- ver of iron in ferropericlase. With these elastic data the lower mantle has been constrained to have 10-15 wt% ferropericlase, which is sufficient to generate some visible effects of spin crossover in seismic tomography. For example, the spin crossover causes that the temperature sensitivity of P wave at the depth of -1700 km is only a fraction of that at the depth of -2300 kin. The disruptions of global P wave structure and of P wave image below hotspots such as Hawaii and Iceland at similar depth are in consistence with the spin crossover effect of iron in ferropericlase. The spin crossover, which causes anomalous ther- modynamic properties of ferropericlase, has also been found to play a control role for the two features of the large low shear velocity provinces （LLSVPs）： the sharp edge and high elevation up to 1000 km above core-mantle boundary. All these results clearly su

关键词： Mantle temperature Mantle composition Composition of Earth's core Ab initio method

Evaluation of Pt and Au pressure scales based on MgO absolute pressure scale

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Science China Earth Sciences 2017年第1期60卷 114-123页

作者： wu zhongqing LIN Feng Laboratory of Seismology and Physics of Earth 's Interior School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China National Geophysical Observatory Mengcheng 233527 China

The equations of state(EOSs)of MgO produced by two independent scale-free methods,(1)the simultaneous elastic wave velocity and in situ synchrotron X-ray measurements(Kono et al.,2010;Li et al.,2006)and(2)the first-principles calculations(wu et al.,2008),agree well with each other to at least 150 GPa and 2000 ***,the EOS from first-principles calculations also agrees well with shock wave data,another pressure-scale-free *** agreements strongly support that these EOSs provide reliable absolute pressure *** we evaluate Au and Pt EOSs based on the EOS of wu et al.(2008)using the simultaneously measured volume data of MgO,Au,and Pt from the *** primary pressure scales developed by Tange et al.(2009)and Yokoo et al.(2009)using only pressure-scale-free experimental data of MgO,Au,and Pt produce internal consistent pressure and agree with EOS of wu et al.(2008).The Au EOS by Tsuchiya(2003)works well at room temperature but underestimates pressure at high *** Au EOS by Fei et al.(2007)can well describe thermal *** EOSs of Pt by Holmes et al.(1989)and Ono et al.(2011)work well at both room temperature and high *** results also suggest that the discrepancy between bulk modulus of iron from experiments(Mao et al.,1990)and those from Earth's core(Dziewonski and Anderson,1981)is not originated from the overestimation of pressure by the EOS of Holmes et al.(1989).At high pressure and temperature,pressure uncertainty resulted from volume error becomes similarly important as the accuracy of the pressure scale.

关键词： P-V relation ab initio calculation Pressure standard Clapeyron slope

Thermodynamic properties of wadsleyite with anharmonic effect

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Earthquake Science 2015年第1期28卷 11-16页

作者： zhongqing wu Laboratory of Seismology and Physics of Earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of China Mengcheng National Geophysical Observatory University of Science and Technology of China

The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation. Based on the method developed recently by wu and Wentzcovitch （Phys Rev B 79：104304, 2009） and wu （Phys Rev B 81：172301, 2010）, we are able to further ab initio include anharmonic effect on thermodynamic properties of crystals by one additional canonical ensemble with numbers of particle, volume and temperature fixed （NVT） molecular dynamic simulations. Our study indicates that phonon-phonon interaction causes the renormalized phonon frequencies of wadsleyite decrease with temperature. This is consistent with the Raman experimental observation. The anharmonic free energy of wadsleyite is negative and its heat capacity at constant pressure can exceed the Dulong-Petit limit at high temperature. The anharmonicity still significantly affects thermodynamic properties of wadsleyite at pressure and temperature con- ditions correspond to the transition zone.

关键词： First principles Forsterite Thermalexpansion GriJnisen parameter

高烈度区某医院建筑基于满足中震正常使用要求的减震结构设计

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广东土木与建筑 2024年第9期31卷 57-61,66页

作者：田小霞李锦铭吴仲青广东省城乡规划设计研究院科技集团股份有限公司广州510290

位于8度抗震设防地区的某医院建筑为钢筋混凝土框架结构,需保证发生本区域设防地震时能够满足正常使用要求。以本医院建筑结构为例,对满足中震正常使用的减震结构设计方法进行研究。从结构变形和承载力两个方面,对现行规范、规程中对中... 详细信息

位于8度抗震设防地区的某医院建筑为钢筋混凝土框架结构,需保证发生本区域设防地震时能够满足正常使用要求。以本医院建筑结构为例,对满足中震正常使用的减震结构设计方法进行研究。从结构变形和承载力两个方面,对现行规范、规程中对中震正常使用的性能要求进行对比和总结。探讨了层间位移角限值要求对结构刚度、附加阻尼比需求的影响,和性能要求对构件承载力设计的影响,得知中震作用下的结构最大层间位移角限值要求对构件截面的选择与布置起较大的控制作用。并采用SAUSAGE有限元分析软件对本工程进行设防地震下的弹塑性时程分析。建议高烈度区的钢筋混凝土框架减震结构,构件承载力验算可采用《高层建筑混凝土结构技术规程:广东省标准DBJ/T 15-91—2021》的中震设计方法,通过对结构刚度、构件承载力合理设计和中震下的构件性能评价,能达到设防地震作用下结构“基本完好、轻微损坏”的性能目标,保证结构在中震下的正常使用要求。

关键词：高烈度地区设防地震消能减震正常使用层间位移角中震设计性能水平

First-principles investigation of the concentration effect on equilibrium fractionation of Ca isotopes in forsterite

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Acta Geochimica 2019年第4期38卷 497-507页

作者： Yahui Song Yonghui Li Wenzhong Wang zhongqing wu Laboratory of Seismology and Physics of Earth’s Interior School of Earth and Space Sciences University of Science and Technology of China

Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca *** results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/***,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a *** the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64

关键词： Ca isotope First-principles calculations Forsterite Concentration effect Equilibrium isotope fractionation

Elasticity of high-pressure clinoenstatite under mantle conditions:Implications for the origin of the X-discontinuity

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Science China Earth Sciences 2023年第4期66卷 718-729页

作者： Jian SONG Wangsheng QIAN Shangqin HAO Wenzhong WANG Daoyuan SUN zhongqing wu Laboratory of Seismology and Physics of Earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Department of Earth Sciences University College LondonLondon WC1E 6BTUnited Kingdom Earth and Planets Laboratory Carnegie Institution for ScienceWashington DC 20015USA CAS Center for Excellence in Comparative Planetology University of Science and Technology of ChinaHefei 230026China National Geophysical Observatory at Mengcheng Mengcheng 233527China

The X-discontinuity is characterized by 2–8% wave impedance contrasts and indistinguishable seismological Clapeyron slopes. Its origin is not yet entirely understood and attributed to a variety of plausible causes, among which the coesite-stishovite transition is a popular mechanism due to its large impedance contrasts. However, the sole coesite-stishovite transition is insufficient to explain indistinguishable seismological Clapeyron slopes of the X-discontinuity. The orthopyroxene(OPX) to high-pressure clinopyroxene(HPCPX) transition has been excluded as a candidate mechanism in recent seismic studies because it can only cause small impedance contrasts based on the first-order estimate from the Birch’s law without direct sound velocity measurements. In this study, we performed first-principles calculations to obtain the elasticity of high-pressure clinoenstatite at high pressure and temperature. Our results show that the impedance contrast caused by the OPX-HPCPX transition is ~5.7% for P wave and ~6.9% for S wave, which are much larger than the previous empirical estimation and hence cannot be ignored. Given that eclogite is subject to partial melting in hot or wet regions, which will promote the enrichment of orthopyroxene by consuming silica, we suggested that both the coesite-stishovite transition and the OPX-HPCPX transition may be dominant mechanisms for the X-discontinuity, with the former dominating where eclogite is hard to melt and the latter dominating where partial melting of eclogite occurs. The model is consistent with seismological observations, indicating the important role of the OPX-HPCPX transition in the X-discontinuity and extensive occurrence of partial melting of eclogite. The proposed origin of the X-discontinuity provides a plausible way to illuminate the melting situation of eclogite in the deep earth.

关键词： X-discontinuity OPX-HPCPX transition High-pressure clinoenstatite Partial melting of eclogite First-principles calculations

Elastic properties of Fe-bearing Akimotoite at mantle conditions: Implications for composition and temperature in lower mantle transition zone

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Fundamental Research 2022年第4期2卷 570-577页

作者： Yajie Zhao zhongqing wu Shangqin Hao Wenzhong Wang Xin Deng Jian Song Laboratory of Seismic and Physics of Earth's Interior School of Earth and Space SciencesUniversity of Seience and Technology of ChinaHefei 230026China National Geophysical Observatory at Mengcheng University of Science and Technology of ChinaHefeiChina CAS Center for Excllence in Comparative Planetology UsTcHefei 230026China Institute of Geophysics and Planetary Physics Scripps Institution of OeanographyUniversiy of California San DiegoLa Jolla 92092CAUSA Departnent of Earth Sciences University CollegeLondonLondon WCIE6BTUnited Kingdom Earth and Planets Laboratory Carnegie Instution for ScienceWashingtonDC 20015UsA

The pyrolite model,which can reproduce the upper-mantle seismic velocity and density profiles,was suggested to have significantly lower velocities and density than seismic models in the lower mantle transition zone(MTZ).This argument has been taken as mineral-physics evidence for a compositionally distinct lower ***,previous studies only estimated the pyrolite velocities and density along a one-dimension(1D)geotherm and never considered the effect of lateral temperature *** the majorite-perovskite-akimotoite triple point is close to the normal mantle geotherm in the lower MTz,the lateral low-temperature anomaly can result in the presence of a significant fraction of akimotoite in pyrolitic lower *** this study,we reported the elastic properties of Fe-bearing akimotoite based on first-principles *** with literature data,we found that the seismic velocities and density of the pyrolite model can match well those in the lower MTZ when the lateral temperature heterogeneity is modeled by a Gaussian distribution with a standard deviation of~10o K and an average temperature of dozens of K higher than the triple point of *** suggest that a harzburgite-rich lower MTZ is not required and the whole mantle convection is expected to be more favorable globally.

关键词： Akimotoite Pyrolite Elasticmoduli Temperature heterogeneity Gaussian distribution

Thermal stability and optical properties of a novel Tm^(3+) doped fluorotellurite glass

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Journal of Rare Earths 2014年第12期32卷 1154-1161页

作者：成茵吴钟晴胡茜吴腾宴周伟伟 College of Physics and Electronic Science Changsha University of Science & Technology

A series of fluorotellurite glasses based on（81–x）Te O2-（10＋x）KF-9La2O3（TKL）, where x=0 mol.%, 5 mol.%, 10 mol.%, 15 mol.%, doped with 2000 ppm Tm2O3, were prepared by the conventional melt quenching *** influence of KF content on the thermal stability and optical spectroscopic properties of the Tm3＋ doped fluorotellurite glasses were investigated by differential scanning calorimetry（DSC）, X-ray diffraction（XRD）, density measurement, Fourier transform infrared spectroscopy（FTIR）, UV-VIS-NIR optical spectroscopy and fluorescence ***-Ofelt intensity parameters of Tm3＋ in as-prepared glasses were determined and used to calculate the spontaneous emission probabilities and the radiative lifetime for the 4f-4f transitions of the Tm3＋ *** emission cross sections in the 1470 nm region（σse） were evaluated by Füchtbauer-Ladenburg *** results showed that KF substitution of Te O2 was beneficial to improving the thermal stability, decreasing glass density and reducing the content of OH related groups for the investigated fluorotellurite *** glass with composition of 66 Te O2-25KF-9La2O3（named TKL25） had the longest radiative lifetime of the 3H4（361 μs） and the largest FWHM×σse value（420.07×10–28 cm3）, which made it a promising material for S-band fiber amplifiers.

关键词： fluorotellurite glass thulium doped thermal stability spectroscopy rare earths

Hydrous plumes in the Archean and the origin of continents

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Science Bulletin 2022年第20期67卷 2023-2025,M0003页

作者： zhongqing wu Guochun Zhao Deep Space Exploration Laboratory/School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Comparative Planetology University of Science and Technology of ChinaHefei 230026China National Geophysical Observatory at Mengcheng University of Science and Technology of ChinaMengcheng 253500China Department of Earth Sciences the University of Hong KongHong KongChina Department of Geology State Key Laboratory of Continental DynamicsNorthwest UniversityXi’an 710029China

The origin of continents,which is fundamentally important in understanding the evolution of Earth and its habitability,remains a highly debatable *** dominant rock types of Archean cratons are tonalite-trondhjemite-granodiorite(TTG)*** evidence suggests that Archean TTG rocks were formed from a hydrous mafic source[1-3].Subduction has been considered to be the only effective means of transporting a great amount of water to the mantle,leading to partial melting to generate a hydrous mafic crust,which can be regarded as the most possible source of the Archean TTG ***,Arndt[2]argued that subduction zones are probably the sole setting in Earth to provide the three main ingredients of the Archean TTG。

关键词： Earth source mantle