First principles investigation of the postspinel transition in Mg2SiO4
First principles investigation of the postspinel transition in Mg2SiO4
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DOI：
10.1029/2007gl029462
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发表时间：
2007-05
影响因子：
5.2
通讯作者：
Yonggang G. Yu;R. Wentzcovitch;T. Tsuchiya;K. Umemoto;D. Weidner
中科院分区：
文献类型：
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作者：
Yonggang G. Yu;R. Wentzcovitch;T. Tsuchiya;K. Umemoto;D. Weidner
我们已经研究了无铁的ringwoodite，Mg 2SiO 4 γ-尖晶石，分解成MgO方镁石和MgSiO 3钙钛矿，使用局域密度近似（LDA）和广义梯度近似（GGA）内的准谐波自由能计算。从GGA获得的转变压力Ptr比LDA对应物更高，并且与实验测量结果吻合得更好。这可以通过仔细检查GGA和LDA函数形式来合理化。由此计算得到的克拉珀龙斜率为−2.9 − −2.6 MPa/K。令人惊讶的是，我们发现一个小的减少，在整个过渡体声速。我们的结果与过渡区底部64 ± 12%的林伍德石体积分数一致。
We have investigated the dissociation of iron free ringwoodite, Mg2SiO4γ‐spinel, into MgO periclase and MgSiO3 perovskite using quasi‐harmonic free energy computations within the local density approximation (LDA) and generalized gradient approximation (GGA). The transition pressure, Ptr, obtained from GGA is higher and in much better agreement with experimental measurements than its LDA counterpart. This can be rationalized by close inspection of GGA and LDA functional forms. The Clapeyron slope obtained from this calculation is −2.9 − −2.6 MPa/K. Surprisingly, we find a small decrease in bulk sound velocity across this transition. Our results are consistent with 64 ± 12% ringwoodite volume fraction at the bottom of the transition zone.