Equation of state and high‐pressure phase transitions of stishovite (SiO2): Ab initio (periodic Hartree‐Fock) results
Equation of state and high‐pressure phase transitions of stishovite (SiO2): Ab initio (periodic Hartree‐Fock) results
复制标题
石英石 (SiO2) 的状态方程和高压相变：从头算（周期 Hartree-Fock）结果
DOI：
10.1029/93jb00783
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发表时间：
1993
影响因子：
--
通讯作者：
D. Sherman
中科院分区：
文献类型：
--
作者：
D. Sherman
The possibility that free SiO{sub 2} may exist at the core mantle boundary motivates a first-principles investigation of the equation of state and possible phase transitions of stishovite using periodic Hartree-Fock theory. Using a moderately extended basis set, the calculated equation of state is shown to be in close agreement with experimental results taken under hydrostatic conditions. When fit to a third-order Birch-Murnaghan equation, the Hartree-Fock total energies give V{sub 0} = 46.1 A{sup 3}, K{sub 0} = 328 GPa, and K{prime} = 4.0. Moreover, the calculated equation of state is very close to that recently obtained using the linearized augmented plane wave method. The bonding in stishovite is unchanged by compression to 80% of its zero-pressure volume (corresponding to a pressure near 110 GPa). The possibility that stishovite might transform to a denser phase at high pressure is investigated by calculating the free energy of SiO{sub 2} in the modified-fluorite and {alpha}-PbO{sub 2} structures. The enthalpy of SiO{sub 2} with the fluorite and modified-fluorite structure is too high to allow those structures to be adopted. The 0 K enthalpy of silica in the {alpha}-PbO{sub 2} structure is within 10 kJ/mol of that of stishovite, and a transition to suchmore » a structure cannot be ruled out in the temperature regime of the lower mantle. However, the density of {alpha}-PbO{sub 2} structure SiO{sub 2} is only 2% greater than that of stishovite. 41 refs., 9 figs., 2 tabs.« less
The possibility that free SiO{sub 2} may exist at the core mantle boundary motivates a first-principles investigation of the equation of state and possible phase transitions of stishovite using periodic Hartree-Fock theory. Using a moderately extended basis set, the calculated equation of state is shown to be in close agreement with experimental results taken under hydrostatic conditions. When fit to a third-order Birch-Murnaghan equation, the Hartree-Fock total energies give V{sub 0} = 46.1 A{sup 3}, K{sub 0} = 328 GPa, and K{prime} = 4.0. Moreover, the calculated equation of state is very close to that recently obtained using the linearized augmented plane wave method. The bonding in stishovite is unchanged by compression to 80% of its zero-pressure volume (corresponding to a pressure near 110 GPa). The possibility that stishovite might transform to a denser phase at high pressure is investigated by calculating the free energy of SiO{sub 2} in the modified-fluorite and {alpha}-PbO{sub 2} structures. The enthalpy of SiO{sub 2} with the fluorite and modified-fluorite structure is too high to allow those structures to be adopted. The 0 K enthalpy of silica in the {alpha}-PbO{sub 2} structure is within 10 kJ/mol of that of stishovite, and a transition to suchmore » a structure cannot be ruled out in the temperature regime of the lower mantle. However, the density of {alpha}-PbO{sub 2} structure SiO{sub 2} is only 2% greater than that of stishovite. 41 refs., 9 figs., 2 tabs.« less