理论计算阳离子对水体中B(OH)_3和B(OH)_4~-间硼同位素平衡分馏的影响

采用密度泛函方法模拟了阳离子对水体中B(OH)3和B(OH)4-的影响,计算海水的硼同位素平衡分馏参数。模拟海水环境时,选择基于分子簇模型的"水滴"法,以最多12个水分子环绕兴趣分子的方式构建"水滴"。对海水环境的计算结果显示,B(OH)3和B(OH)4-的硼同位素平衡分馏系数在25?C时为1.031,与纯水环境下的该分馏值并无明显差别。研究表明前人对B(OH)3和B(OH)4-间硼同位素平衡分馏参数的实验测定可能存在问题。研究结果为精进硼同位素古环境重建工作和硼同位素平衡分馏测定提供了理论制约。     

硼掺入Mg(OH)2形式及机理

采用pH=9.5～13.0的无镁合成海水进行了Mg(OH)₂沉积时B的掺入实验,证实了B(OH)₃优先掺入Mg(OH)₂的硼同位素分馏特征。在所研究的pH范围内,Mg(OH)₂沉积的δ11B均高于无镁合成海水的δ11B,它们之间的硼同位素分馏系数α沉积/海水为1.017 7~1.056 9,平均为1.032 9±0.009 32(SD)。硼同位素的这种分馏特征与无机碳酸盐沉积时的硼同位素分馏存在明显差异,表明B掺入Mg(OH)₂沉积具有不同的机理。B在Mg(OH)₂沉积上的吸附以及B(OH)₃与Mg(OH)₂的沉积反应同时存在并相互制约是其主要特征,造成了B(OH)₃优先掺入的总结果,这并不意味B(OH)₃在掺入的分数上占有优势,相反在所研究的pH范围内,Mg(OH)₂沉积的B(OH)₃/B(OH)-₄大都小于1,因此吸附作用决定了Mg(OH)₂沉积中B浓度的变化特征。采用这种模型能很好地解释沉积中B浓度、B在沉积和海水间的分配系数Kd以及沉积与海水间的分馏系数α随海水pH的变化特征。石珊瑚中Mg(OH)₂的普遍存在和Mg(OH)₂中B(OH)₃的优先掺入也许会影响珊瑚的硼同位素组成与海水pH的定量对应关系,给δ11B作为古海水pH的代用指标带来一定的不确定性。     

几个重要Ge同位素平衡分馏参数的理论预测

本研究基于Urey模型(或称Bigeleisen和Mayer公式),结合量子化学计算的方法,在B3LYP/6-311+G(d, p)理论水平下,计算了Ge在类似石英(包括蛋白石)、钠长石、钾长石、橄榄石结构以及水溶液(包括海水)中Ge(OH)4和GeO(OH)3-之间的Ge同位素平衡分馏系数.其中,溶液效应用"水滴法"处理,矿物结构用簇合物方法模拟.结果显示这些基本分馏参数的精度约±0.3‰;类石英(或蛋白石)结构最可能富集重Ge同位素,在25 ℃,几个Ge同位素分馏系数分别约为:Δ石英-Ge(OH)4=0.9‰、ΔGe(OH)4-GeO(OH)3-=0.3‰(海水中)、Δ石英-钠长石=0.6‰、Δ石英-钾长石=0.4‰、Δ橄榄石-Ge(OH)4=-1.2‰.类石英与类橄榄石结构之间存在较大的分馏,Δ石英-橄榄石=2.1‰.这些具有重要地质意义的基本分馏参数可以为探索未知的Ge同位素地球化学应用领域打下基础.此外,本文还用所得的分馏参数定量地解释了Siebert等(2006)和Rouxel等(2006)的一些工作,说明了这些参数的可靠性及其在地学中的重要应用意义.     

硼同位素分馏的实验理论认识和矿床地球化学研究进展

硼是一种中等挥发性元素,具有¹¹B和¹⁰B两个稳定同位素。两个同位素间高达10%的相对质量差使其在地质过程中引起高达-70‰至+75‰的硼同位素变化。硼在自然界主要与氧键合形成三配位(BO₃)和四配位(BO₄)结构,因而¹¹B和¹⁰B间同位素分馏主要受控于三配体(BO₃)和四面体(BO₄)间配分。本文综述了低温和高温地质过程的硼同位素分馏的理论和实验研究进展。在溶液中B(OH)₃和${B(OH)^{-}_{4}}$间硼同位素分馏受pH和热力学p-T条件控制,实验和理论表征获得常温常压条件下的B(OH)₃和$B(OH)^{-}_{4}$间同位素分馏系数(α_3-4)变化范围为1.019 4至1.033 3。低温条件下矿物(如碳酸盐、黏土矿物(蒙脱石和伊利石)、针铁矿、水锰矿、硼酸盐)与溶液间硼同位素分馏行为除了受p-T-pH影响外,矿物表面吸附引起的分馏效应十分显著。在中高温过程(蒙脱石伊利石化、富硼电气石和白云母矿物与热液流体,以及硅酸盐熔体与流体)中硼同位素分馏行为受到硼配位构型、化学成分以及物理化学条件的控制。随着硼同位素分馏机理研究的深入以及越来越完善的地质储库硼同位素端员特征表征,硼同位素地球化学指标可以灵敏示踪成矿物质来源、探究成矿作用与成因模式和重建成矿过程物理化学条件。目前矿床硼同位素地球化学研究的难点在于实现不同赋存相(如流体、矿物和熔体)中硼配位键合结构和硼同位素组成的精细化表征。     

Partial Hessian Vibrational Analysis(PHVA)的原理、方法及在地质学中的应用

PHVA在简化模型大小,提高计算效率在计算科学有重要的地位.应用PHVA方法可以求分子簇模型兴趣区的简谐频率,可以用来研究超大分子或矿物的局部振动性质,可用于化学反应动力学及同位素分馏系数计算等.     

富有机物流体中一些重要Ge同位素的平衡分馏参数

锗（Ge）同位素在地球化学领域有着潜在的应用意义,但是Ge同位素平衡分馏参数的缺乏,严重制约了其在相关研究中的应用。本研究提供了富有机物流体中物种Ge（OH）4、GeO（OH）3^-以及Ge的一些亲有机质络合物（Ge与邻苯二酚、柠檬酸以及草酸配合形成的络合物）之间的Ge同位素平衡分馏参数。用基于Urey模型（或称Bigeleisen-Mayer公式）理论,结合量子化学计算的方法,在B3LYP／6-311＋G（d,p）理论水平下计算了这些Ge同位素平衡分馏系数,其中,溶液效应用精确的“水滴法”来处理。预测这些基本分馏参数的误差约为±0．2‰。纯水溶液中,△Ge（OH）4-GeO（OH）3^-约为0．6‰,海水中稍小,约为0．3‰;而△Ge（OH）4-Ge-邻苯二酚、△Ge（OH）4-Ge-草酸、△Ge（OH）4-Ge-柠檬酸（c）和△Ge（OH）4-Ge柠檬酸（d）非常大,分别约为4．4‰、3．5‰、3．8‰和3．9‰。这些大的分馏或许可以用来示踪生物作用参与过程。结果表明,轻的Ge同位素将富集在富有机质的环境,如煤系、黑色页岩及一些缺氧的条件下,因此这些环境可能存在一个轻Ge同位素的“汇”。     

近十年中国同位素效应理论和计算研究进展

近十年来,国内稳定同位素地球化学的理论解释已普遍达到了量子化学水平.基于精密的量子化学从头或第一性原理,研究者们开始了平衡和动力学分馏系数的计算.在同位素的分析测试、野外观察、理论和计算四个方向上,国内在理论和计算方向的发展可能还算最好的,整体处于国际第一方阵的地位.国内学者率先发展了超冷体系同位素分馏、含压力效应的同位素分馏、同位素的浓度效应、团簇同位素、微小同位素异常、热梯度下同位素扩散效应、高温重复过程等方向的同位素理论和计算方法,也发展了针对固-液两相同位素分馏的可变体积的分子簇(VVCM)计算新方法、针对重金属同位素固相体系的含核体积效应处理的方法,以及针对熔体中同位素扩散的动力学分馏的理论和计算方法.同时,还为大量不同的非传统(金属)同位素体系,提供了大量的平衡分馏系数,为这些同位素体系的日后深入应用奠定了较好的基础.但是,在这些成果中,真正由我国学者首先提出的原始概念、模型、体系和方法还很少,绝大多数都是对前人(主要是国外同行)提出的理论体系和新兴发展方向的修改和补充.未来我国同位素理论和计算领域应率先使用包含量子场论在内的新一代理论工具,在同位素效应的新方向、新概念的提出和新理论的建立方面,做出更多的贡献.     

用分子簇模型计算矿物的稳定同位素分馏的一个问题

簇合物模型(Cluster Model)已经被广泛地用来模拟矿物的局域结构和物理化学性质.但是,在计算矿物稳定同位素平衡分馏时,是否忽略平动和转动能还存在分歧.本文通过理论推导和对实际体系的计算研究了这一问题,详细评估了平动和转动能在配分函数之比中的贡献,给出了可以忽略的条件,说明在一般情况下,应用分子簇方法研究矿物的同位素分馏时,不应该忽略平动和转动能的贡献.     

活体珊瑚微量元素对硼同位素组成影响及硼掺入珊瑚的形式

为确定元素 B 掺入进珊瑚的形式、B(OH)与 B(OH)3间的分馏系数及珊瑚中微量元素对硼同位素?4组成的影响,对北海涠洲岛、海南三亚和雷州半岛灯楼角三地活体珊瑚的 Mg、Sr、Na、Ca、B 浓度及硼同位素组成(δ11Bcoral)进行了测定.结果表明,涠洲岛、三亚和灯楼角三地珊瑚的 Mg、Sr、Na 和 Ca 浓度平均值分别为40.1 mmol/L、86.1 mmol/L、449 mmol/L 和12.1 mol/L.珊瑚中 B 浓度的变化范围为4.4~8.4 mmol/L,平均值为5.9 mmol/L.Ca、Sr 在珊瑚中明显富集,而 Mg 在珊瑚中贫化.珊瑚 B 浓度的变化主要反映了珊瑚生长时海水 pH 值的变化.δ11Bcoral 的变化范围为22.8‰~27.9‰,平均为25.2‰.除与 B 浓度呈弱正相关关系外,δ11Bcoral 与其他四种元素不相关.应用珊瑚硼同位素组成恢复古海水 pH 值时选择同属种珊瑚和判别是否有 Mg(OH)2的存在是必要的.涠洲岛、灯楼角和三亚三地珊瑚与海水间的硼同位素分馏系数αcoral-sw 分别为0.9839、0.9847和0.9850.计算得到的珊瑚与海水 B(OH)3间的分馏系数αcoral-3的变化范围为0.9772~0.9800,平均值为0.9788.该新的α4-3值是准确的,可以用来反演古海水 pH 值.αcoral-sw 和αcoral-3随pH 值的升高分别呈现出增大和减小的变化趋势.珊瑚的平均δ11Bcoral 位于理论计算的δ11B4和δ11B3曲线之间,而且都低于原始合成海水的δ11B.这些都表明 B 以 B(OH)3和B(OH)两种形式以变化的比例同时掺入进?4珊瑚,并以B(OH)优先掺入为主.计算得到有0.1%~5.5%(平均值为2.2%)的 B(OH)3掺入进珊瑚中.由于?4 B(OH)3同时掺入进生物碳酸盐,δ11Bcarb=δ11B4的假设不能成立,由所测生物碳酸盐δ11Bcarb 值计算的海水 pH值将产生误差,使δ11B-pH 技术变得更为复杂.通过无机碳酸盐沉积或有孔虫或珊瑚的养殖实验(或者野外观测实验)建立用于重建古海水 pH 值的δ11Bcarb-pH 经验方程是今后的一项重要任务.     

海水蒸发时的硼同位素分馏

采用立式亚沸石英蒸馏器，在非流动条件下进行了海水蒸发实验，以研究海水一空气界面硼同位素的行为。将具有不同pH值的天然海水在不同温度下平静地蒸发，采用冷水收集海水蒸汽，实现了无流动空气的真实的蒸发过程，共进行了3种类型的实验。 实验1 将不同pH值（(7.71-8.49)的海水在27℃，33℃和40℃下蒸发，蒸发时连续地补充高纯水以维持蒸发液体的体积恒定。收集海水蒸汽，进行蒸汽的硼同位素组成、硼和氯浓度的测定。 实验2将天然海水在33℃下蒸发，蒸发时不补加高纯水．搏派承药蒸干。分捌收集海水蒸汽和蒸干后的固体盐，进行蒸汽和固体盐的硼同位素组成测定。并同时测定不同蒸发阶段海水的pH值。 实验3 将加人不同硼量的天然海水在40℃下蒸发.蒸发时连续地补充高纯水以维持蒸发液体的体积恒定，收集海水蒸汽，进行硼同位素和硼浓度的测定。 硼浓度的结果表明：①在实验1中，蒸汽的硼浓度变化范围是1.51-10.7 μg/L，平均值为5.16 μg/L，随海水pH值升高而降低，但与蒸发温度无关；②在实验2和3中蒸汽硼的浓度要远远高于实验1，而且蒸汽硼浓度与海水硼浓度具有线性的正相关关系；③蒸汽相的Cl/B比（摩尔比值：平均23.4)远远低于海水的Cl/B比（摩尔比值：1485)，这表明蒸发时没有将海水喷雾的细珠引人蒸汽中。 硼同位素结果表明： (1)在实验1中，蒸汽的δ11B值除一个以外均低于海水B(OH)3的δ11B值，而高于海水B(OH)4-的δ11B值，而且都比海水的δ11B值高，蒸汽与海水间的平均硼同位素分馏系数为1.0019，这表明在海水蒸发时，11B富集在蒸汽相中。此结果与以前所进行的硼溶液蒸发实验结果一致，但与以前所进行的海水蒸发实验结果完全相反。以前的海水蒸发实验结果表明，10B在蒸汽相富集。这种截然相反的结果要归结于蒸发条件的差异，以前蒸发的海水蒸汽是由流动空气带出，此时非平衡的动力因素将起到重要作用，造成质量轻的10B优先进人蒸汽相。而本次实验在非空气流动条件下进行，B(OH)3和B(OH)-4间的同位素平衡将起主导作用。显然，燕汽的δ11B值与海水的pH值没有明显的关系。 (2)在实验2中，蒸汽与海水间的硼同位素分馏系数要远远高于实验1，特别当海水蒸干前的500 mL蒸汽，分馏系数高达1.0182。而蒸干后的固体盐的δ11B值明显低于原始海水，分馏系数为0.9973。这充分表明，在海水蒸发时，11B优先被蒸发而进人燕汽相。海水蒸发时蒸汽相的δ11B值随蒸发程度呈平方指数形式增加，这与蒸发时残留海水的δ11B值急剧升高有关。 (3）实验3中，蒸汽的δ11B值随海水硼浓度的增加而升高，当硼浓度为19.7 μg/mL和63.5 μg/mL时，硼同位素分馏系数分别为1.0072和1.0107。 海水蒸发时的硼同位素分馏可用于对大气降雨硼来源的研究。在不同时期采集的西宁雨水的δ11B值为12.1‰和9.0‰，受风向的影响甚微，表明西宁地区的大气环境受海洋影响较小，大气中的硼主要来源于陆地。但南海西江石油平台大气降雨的δ11B值明显受风向所控制，高δ11B值（33.2‰）表明其海洋来源，而低δ11B值（8.4‰）表明其陆地来源。以往文献所报道的陆地及其沿海大气降雨的δ11B值变化范围很宽(0.8‰~35‰)，但是它们都低于海水的δ11B值，这表明陆地及其沿海大气中的硼主要来源于陆地。 海水中的硼将因洋壳低温蚀变、沉积物吸附以及生物碳酸盐共沉淀从海洋中迁出，这些过程均造成海水10B的贫化。惟独海水蒸发时会造成海水10B的富集，但由于此时硼同位素分馏小，而且与其他因素相比，被海水蒸汽迁出的硼量低，根据计算，海水燕发对古海洋硼同位素组成的影响完全可以忽略不计。     

Interaction of B(OH)_3^0 and HCO_3^ - in Seawater: Formation of B(OH)_2 CO_3^ -

Boron is known to interact with a wide variety of protonated ligands(HL) creating complexes of the form B(OH)₂L^-.Investigation of the interaction of boric acid and bicarbonate in aqueoussolution can be interpreted in terms of the equilibrium $B(OH)_3^0 + HCO_3^ - \rightleftharpoons B(OH)_2 CO_3^ - + H_2 O$ The formation constant for this reaction at 25 °C and 0.7 molkg^-1 ionic strength is $K_{BC} = \left[ {B(OH)_2 CO_3^ - } \right]\left[ {B(OH)_3^0 } \right]^{ - 1} \left[ {HCO_3^ - } \right]^{ - 1} = 2.6 \pm 1.7$ where brackets represent the total concentration of each indicatedspecies. This formation constant indicates that theB(OH)₂ $CO_3^ - $ concentration inseawater at 25 °C is on the order of 2 μmol kg^-1. Dueto the presence of B(OH)₂ $CO_3^ - $ , theboric acid dissociation constant ( $K\prime _B $ ) in natural seawaterdiffers from $K\prime _B $ determined in the absence of bicarbonate byapproximately 0.5%. Similarly, the dissociation constants of carbonicacid and bicarbonate in natural seawater differ from dissociation constantsdetermined in the absence of boric acid by about 0.1%. Thesedifferences, although small, are systematic and exert observable influenceson equilibrium predictions relating CO₂ fugacity, pH, totalcarbon and alkalinity in seawater.     

Stable boron isotope fractionation between dissolved B(OH)3 and B(OH)4

The stable boron isotope ratio (¹¹B/¹⁰B) in marine carbonates is used as a paleo-pH recorder and is one of the most promising paleo-carbonate chemistry proxies. Understanding the thermodynamic basis of the proxy is of fundamental importance, including knowledge on the equilibrium fractionation factor between dissolved boric acid, B(OH)₃, and borate ion, B(OH)₄⁻ (, hereafter α_(B3-B4)). However, this factor has hitherto not been determined experimentally and a theoretically calculated value (Kakihana and Kotaka, 1977, hereafter KK77) has therefore been widely used. I examine the calculations underlying this value. Using the same spectroscopic data and methods as KK77, I calculate the same α_(B3−B4) = 1.0193 at 300 K. Unfortunately, it turns out that in general the result is sensitive to the experimentally determined vibrational frequencies and the theoretical methods used to calculate the molecular forces. Using analytical techniques and ab initio molecular orbital theory, the outcome for α_(B3-B4) varies between ∼1.020 and ∼1.050 at 300 K. However, several arguments suggest that α_(B3-B4) ? 1.030. Measured isotopic shifts in various ¹⁰B-, ²D-, and ¹⁸O-labeled isotopomers do not provide a constraint on stable boron isotope fractionation. I conclude that in order to anchor the fundamentals of the boron pH proxy, experimental work is required. The critics of the boron pH proxy should note, however, that uncertainties in α_(B3-B4) do not bias pH reconstructions provided that organism-specific calibrations are used.     

氢氧化镁处理含铬废水的研究

用硫酸亚铁将废水中Ｃｒ（Ⅵ）还原成Ｃｒ（Ⅲ）,再用氢氧化镁乳液和废水中的酸,使铬离子,铁离子氢氧化物沉淀,澄清分离,这样含铬废水经处理后,铬的含量及ｐＨ值有达到排放标准,该方法操作简便,效果显著。     

1Tc-Strontiohilgardit (Ca,Sr)2[B5O8(OH)2Cl] und seine Stellung in der Hilgarditgruppe X2/II[B5O8(OH)2Cl]

Zusammenfassung 1Tc-Strontiohilgardit (Ca, Sr)₂ [B₅O₈(OH)₂,Cl] mit Ca : Sr etwa 1 : 1 ist ein neues Mineral der Hilgarditgruppe. Fundpunkt: Reyersbausen (9° 59,7 E, 51° 36,6 N), Grube Königshall-Hindenburg, Flöz Staßfurt in sylvinitischer Ausbildung.Konstanten : triklin-pedial,a ₀=6,38 Å,b ₀=6,480 Å,c ₀=6,608 Å, =75,4°,=61,2°, =60,5°; tafelige-gestreckte Links- und Re chtskristalle, farblos, wasserunlöslich, piezoelektrisch. Härte 5–7, Dichte 2,99 g cm^–3;n =1,638,n =1,639,n =1,670; 2V =19°.Neue Daten für die Hilgarditgruppe : 2 M (Cc)-Calciumhilgardit (=Hilgardit) =4 Ca₂[B₅O₃(OH)₂Cl], Raumgruppe Cc.3Tc-Calciumhilgardit (=Parahilgardit) = 3 Ca₂[B₅O₃(OH)₂Cl]; trinklin-pedial, ₀=6,31 Å,b =6,484 Å,c ₀=17,50 Å; =84,0°,=79,6°, =60,9°.Die Polymorphiebeziehungen sind geometrisch deutbar durch eine spezielle Art der Polytropie (Stapelung von Links- und Rechtskristallen im Elementarbereich).     

利用尾矿砂制备镁铁氢氧化物实验研究

以金川铜镍矿尾矿酸浸液为原料,根据矿物沉淀pH值区间的不同,分步分离Fe、Mg的沉淀物以及有价金属Al、Co、Ni、Cu的混合沉淀物,进而制备具有高附加值的Fe(OH)3和Mg(OH)2,同时富集Co、Ni、Cu等有价金属。结果表明,当溶液pH值为3.8时可沉淀分离出主要成分为施威特曼石(schwertmannite)的氢氧化铁前驱体,pH值达到9.8时沉淀富集出Al、Co、Ni、Cu的混合氢氧化物,随即得到只含有Mg离子的溶液。在60℃条件下,将施威特曼石在pH值为12的NaOH溶液中老化36h,可以得到Fe(OH)3。同时,以NaOH调节只含有Mg离子的溶液至pH值为12.4时可获得Mg(OH)2。本研究为金属矿山尾矿的资源化综合利用提供了新的思路与方法。     

The enthalpy of transformation of Ca(OH)2-I (portlandite) to Ca(OH)2-II (EuI2 structure) by low-temperature DSC

 Thermodynamic properties of high-pressure minerals that are not recoverable from synthesis experiments by conventional quenching methods (“unquenchable” phases) usually are calculated from equation of state data and phase diagram topologies. The present study shows that, with cryogenic methods of recovery and sample treatment, phases with a suitable decomposition rate can be made accessible to direct thermodynamic measurements. A set of samples of Ca(OH)₂-II has been synthesized in a multianvil device and subsequently recovered by cooling the high-pressure assembly with liquid nitrogen. Upon heating from liquid nitrogen to room temperature, the material transformed back to Ca(OH)₂-I. The heat effect of this backtransformation was measured by differential scanning calorimetry. A commercial differential scanning calorimeter (Netzsch DSC 404), modified to allow sample loading at liquid nitrogen temperature was used to heat the material from −150 to +200 °C at rates varying between 5 and 15 °C min⁻¹. The transformation started around −50 °C very gradually, and peaked at about 0 °C. To obtain a baseline correction, each sample was scanned under exactly the same conditions after the backtransformation was complete. Because of the relative sluggishness, onset and offset temperatures were not well defined as compared to fast (e.g., melting) reactions. To aid in integration, the resulting signals were successfully fitted using a generic asymmetric peak model. The enthalpy of backtransformation was determined to be ΔH =−10.37 ± 0.50 kJ mol⁻¹. From previous in situ X-ray diffraction experiments, the location of the direct transformation in P-T space has been constrained to 5.7 ± 0.4 GPa at 500 °C (Kunz et al. 1996). With the reaction volume known from the same study, and assuming that ΔC _p of the transformation remains negligible between the conditions of our measurements and 500 °C, our result gives an estimate of the entropy of transition and the P-T slope of the reaction curve. To a first approximation, the values ΔS = −16.00 ± 0.65 J(mol · K)⁻¹ and dP/dT = 0.0040 ± 0.0002 GPa/K have been determined. These results need to be refined by equation of state data for Ca(OH)₂-II. Received: 30 December 1999 / Accepted: 10 April 2000     

High-pressure properties of diaspore,AlO(OH)

The structural compression mechanism and compressibility of diaspore, AlO(OH), were investigated by in situ single-crystal synchrotron X-ray diffraction at pressures up to 7 GPa using the diamond-anvil cell technique. Complementary density functional theory based model calculations at pressures up to 40 GPa revealed additional information on the pressure-dependence of the hydrogen-bond geometry and the vibrational properties of diaspore. A fit of a second-order Birch–Murnaghan equation of state to the p–V data resulted in the bulk modulus B ₀ = 150(3) GPa and B ₀ = 150.9(4) GPa for the experimental and theoretical data, respectively, while a fit of a third-order Birch–Murnaghan equation of state resulted in B ₀ = 143.7(9) GPa with its pressure derivative B′ = 4.4(6) for the theoretical data. The compression is anisotropic, with the a-axis being most compressible. The compression of the crystal structure proceeds mainly by bond shortening, and particularly by compression of the hydrogen bond, which crosses the channels of the crystal structure in the (001) plane, in a direction nearly parallel to the a-axis, and hence is responsible for the pronounced compression of this axis. While the hydrogen bond strength increases with pressure, a symmetrisation is not reached in the investigated pressure range up to 40 GPa and does not seem likely to occur in diaspore even at higher pressures. The stretching frequencies of the O–H bond decrease approximately linearly with increasing pressure, and therefore also with increasing O–H bond length and decreasing hydrogen bond length. Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.     

Near InfraRed Imaging Spectrograph (NIRIS) for ground-based mesospheric OH(6-2) and $$\hbox {O}_{2}$$(0-1) intensity and temperature measurements

This paper describes the development of a new Near InfraRed Imaging Spectrograph (NIRIS) which is capable of simultaneous measurements of OH(6-2) Meinel and \(\hbox {O}_{2}\)(0-1) atmospheric band nightglow emission intensities. In this spectrographic technique, rotational line ratios are obtained to derive temperatures corresponding to the emission altitudes of 87 and 94 km. NIRIS has been commissioned for continuous operation from optical aeronomy observatory, Gurushikhar, Mount Abu (\(24.6^{\circ }\hbox {N}\), \(72.8^{\circ }\hbox {E}\)) since January 2013. NIRIS uses a diffraction grating of 1200 lines \(\hbox {mm}^{-1}\) and 1024\(\times \)1024 pixels thermoelectrically cooled CCD camera and has a large field-of-view (FOV) of \(80^{\circ }\) along the slit orientation. The data analysis methodology adopted for the derivation of mesospheric temperatures is also described in detail. The observed NIRIS temperatures show good correspondence with satellite (SABER) derived temperatures and exhibit both tidal and gravity waves (GW) like features. From the time taken for phase propagation in the emission intensities between these two altitudes, vertical phase speed of gravity waves, \(c_{z}\), is calculated and along with the coherent GW time period ‘\(\tau \)’, the vertical wavelength, \(\lambda _{z}\), is obtained. Using large FOV observations from NIRIS, the meridional wavelengths, \(\lambda _{y}\), are also calculated. We have used one year of data to study the possible cause(s) for the occurrences of mesospheric temperature inversions (MTIs). From the statistics obtained for 234 nights, it appears that in situ chemical heating is mainly responsible for the observed MTIs than the vertical propagation of the waves. Thus, this paper describes a novel near infrared imaging spectrograph, its working principle, data analysis method for deriving OH and \(\hbox {O}_{2}\) emission intensities and the corresponding rotational temperatures at these altitudes, derivation of gravity wave parameters (\(\tau \), \(c_{z}\), \(\lambda _{z}\), and \(\lambda _{y})\), and results on the statistical study of MTIs that exist in the earth’s mesospheric altitudes.