Quasi-hydrostatic compression of magnesium oxide to 52 GPa: Implications for the pressure-volume-temperature equation of state
Quasi-hydrostatic compression of magnesium oxide to 52 GPa: Implications for the pressure-volume-temperature equation of state
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DOI：
10.1029/2000jb900318
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发表时间：
2001-01-10
影响因子：
3.9
通讯作者：
Mao, HK
中科院分区：
文献类型：
--
作者：
Speziale, S;Zha, CS;Mao, HK
利用能量色散同步辐射X射线衍射仪，以甲醇-乙醇(至10 Gpa)或氦(至52 Gpa)为传压介质，在金刚石顶压室中对方镁石进行了近静水压条件下的室温静态压缩。在所有实验压力范围内，平均相对标准偏差为0.0003，测定了高精度的池参数。固定体积弹性系数K-0 T=160.2 GPA，用三阶Birch-Murnaghan状态方程拟合得到：V-0=74.71+/-0.01Angstrom(3)，(偏导数K(0T)/偏导数P)(T)=3.99+/-0.01。用不同的P-V-T数据对Birch-Murnghhan-Debai热状态方程进行了拟合，得到了Gruneisen参数Gamma(0)=1.49+/-0.03，而不是体积依赖系数Q，热力学理论将其约束为1.65+/-0.4。建立在Q值不变基础上的模型不能解释超高压(P=174-203 Gpa)冲击压缩数据。我们建立了一个模型，其中Q随压缩而减小，从0.1 Mpa时的1.65降至200 Gpa时的0.01。该模型在Mie-Gruneisen-Debai假设的框架内，令人满意地描述了低压静态数据(=0.4%到53 Gpa)和高压Hugoniot数据(<；1%到203 Gpa)。在P=174-203 GPa时，热膨胀系数的平均值在14.1+/-2.8到16.3+/-2.7×10(-6)K-1之间。熔化温度对压力的依赖关系得到初始压力导数T-m/偏导数P=98K/Gpa。我们的分析表明，建立一个简单的Gruneisen参数与体积关系的模型是可能的，该模型可以成功地描述从环境到203 GPa3663K的MgO的P-V-T状态方程。
Room temperature static compression of MgO (periclase) was performed under nearly hydrostatic conditions using energy dispersive synchrotron X-ray diffraction in a diamond anvil cell with methanol-ethanol (to 10 GPa) or helium (to 52 GPa) as a pressure-transmitting medium. Highly precise cell parameters were determined with an average relative standard deviation = 0.0003 over all the experimental pressure range. Fixing the bulk modulus K-0T = 160.2 GPa, a fit of the data to the third-order Birch-Murnaghan equation of state yields: V-0 = 74.71 +/- 0.01 Angstrom (3), (partial derivativeK(0T)/partial derivativeP)(T) = 3.99 +/- 0.01. A fit of different P-V-T datasets, ranging to 53 GPa and 2500 K, to a Birch-Murnghhan-Debye thermal equation of state constrained the Gruneisen parameter gamma (0) = 1.49 +/- 0.03, but not its volume dependence q, which was constrained to 1.65 +/- 0.4 by thermodynamic theory. A model based on a constant value of q cannot explain the ultrahigh pressure (P = 174-203 GPa) shock compression data. We developed a model in which q decreases with compression from 1.65 at 0.1 MPa to 0.01 at 200 GPa. This model, within the framework of the Mie-Gruneisen-Debye assumptions, satisfactorily describes the low-pressure static data ( = 0,4% to 53 GPa) and the high-pressure Hugoniot data ( < 1% to 203 GPa). Average values of the thermal expansion coefficient a range between 14.1 +/- 2.8 and 16.3 +/- 2.7 x 10(-6) K-1 at P = 174-203 GPa. The pressure dependence of the melting temperature yields an initial pressure derivative T-m/partial derivativeP = 98 K/GPa. Our analysis shows that it is possible to develop a simple model of the volume dependence of the Gruneisen parameter that can successfully describe the P-V-T equation of state of MgO from ambient conditions to 203 GPa and 3663 K.