Compressibility of protoamphibole: A high-pressure single-crystal diffraction study of protomangano-ferro-anthophyllite
Compressibility of protoamphibole: A high-pressure single-crystal diffraction study of protomangano-ferro-anthophyllite
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原角闪石的可压缩性：原锰酸铁直闪石的高压单晶衍射研究
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发表时间：
2010
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通讯作者：
D. Pasqual
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作者：
P. Zanazzi;Fabrizio Nestola;D. Pasqual
用原位单晶X射线衍射法研究了原角闪石(空间群PnmN)在日本赤木县横根山原锰铁叶绿石(Mn1.39Fe0.59)(Fe3.98Mg1.02)Si8O22(OH)2上的高压行为。在不同的压力下收集了单胞参数，最高可达9 Gpa，并从几种压力下收集的数据中获得了结构精细化。用三阶Birch-Murnaghan状态方程对P-V数据进行拟合，得到以下参数：K_(T0)=(1)Gpa，K‘=7.0(4)，V_0=926.4(4)？3.轴向模数为：K_0a=30.7(8)Gpa，K’a=10.8(5)，a_0=9.430(2)；K0c=94(5)，GPA，K‘c=4(1)，c0=5.354(2)？相应的轴向压缩系数(10-3 Gpa-1)分别为βa=10.9(3)、βb=3.1(1)和βc=3.5(2)，表明原锰铁叶绿岩的高压行为是高度各向异性的，最大的压缩系数位于[10 0]方向。在所研究的压力范围内，没有观察到不连续的行为或多态转变。结构精化表明，由于组成相似，M1、M2和M3多面体具有相似的可压缩性。M4(72%Mn，28%Fe)是一个高度扭曲的位置，比其他八面体略软。四面体带中的主要运动涉及双链的扭结，沿[100]方向弯曲通过空的A位，以及四面体旋转，这是与八面体层保持一致所必需的。O5-O6-O5在空气中的扭转角从179.1(2)°下降到6.9GPa174(2)°。在6.9GPa时，T1-O7-T1角从143.8(3)°增加到134(5)°，四面体旋转α从0.2(2)°增加到4(2)°。
Abstract The high-pressure behavior of protoamphibole (space group Pnmn) was studied by in situ singlecrystal X-ray diffraction on a sample of protomangano-ferro-anthophyllite with formula (Mn1.39Fe0.59) (Fe3.98Mg1.02)Si8O22(OH)2, from Yokone-Yama, Awano Town, Tochigi Prefecture, Japan. Unit-cell parameters were collected at various pressures up to 9 GPa, and structural refinements were obtained from data collected at several pressures up to 7 GPa. Fitting the P-V data to a third-order Birch- Murnaghan equation of state (EoS) gives the following parameters: KT0 = 64(1) GPa, K′ = 7.0(4), and V0 = 926.4(4) Å3. Axial moduli are: K0a = 30.7(8) GPa, K′a = 10.8(5), and a0 = 9.430(2) Å; K0b = 109(4) GPa, K′b = 2.7(8), and b0 = 18.364(4) Å; K0c = 94(5), GPa, K′c = 4(1), and c0 = 5.354(2) Å. The corresponding axial compressibilities (10-3 GPa-1) are βa = 10.9(3), βb = 3.1(1), and βc = 3.5(2), and indicate that the HP behavior of protomangano-ferro-anthophyllite is highly anisotropic, the highest compressibility being along [100]. No discontinuous behavior or polymorphic transitions were observed in the pressure range studied. Structural refinements show that M1, M2, and M3 polyhedra have similar compressibilities, owing to their similar composition. M4 (72% Mn, 28% Fe) is a highly distorted site and is slightly softer than the other octahedra. The major movements in the tetrahedral ribbon concern kinking of the double chain, bending along the [100] direction through the empty A site, and tetrahedral rotation, necessary to maintain coherence with the octahedral layer. The kinking angle of O5-O6-O5, which in air is 179.1(2)°, decreases to 174(2)° at 6.9 GPa. The T1-O7-T1 angle changes from 143.8(3)° to 134(5)° at 6.9 GPa, and the tetrahedral rotation α increases from 0.2(2)° to 4(2)°.