Quantum Monte Carlo calculations of the structural properties and the B1-B2 phase transition of MgO

Alfè, Dario; Alfredsson, Maria; Brodholt, John P.; Gillan, M. J.; Towler, M. D.; Needs, R. J.

doi:10.1103/physrevb.72.014114

Cited by 61 publications

(36 citation statements)

References 49 publications

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“…In this work, we use the quantum Monte Carlo (QMC) method (24,25) to compute silica equations of state, phase stability, and elasticity, documenting improved accuracy and reliability over DFT. Our work significantly expands the scope of QMC by studying the complex phase transitions in minerals away from the cubic oxides (26,27). Furthermore, our results have geophysical implications for the role of silica in the lower mantle.…”

Section: Introductionmentioning

confidence: 69%

Quantum Monte Carlo computations of phase stability, equations of state, and elasticity of high-pressure silica

Driver

Cohen

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Silica (SiO 2 ) is an abundant component of the Earth whose crystalline polymorphs play key roles in its structure and dynamics. First principle density functional theory (DFT) methods have often been used to accurately predict properties of silicates, but fundamental failures occur. Such failures occur even in silica, the simplest silicate, and understanding pure silica is a prerequisite to understanding the rocky part of the Earth. Here, we study silica with quantum Monte Carlo (QMC), which until now was not computationally possible for such complex materials, and find that QMC overcomes the failures of DFT. QMC is a benchmark method that does not rely on density functionals but rather explicitly treats the electrons and their interactions via a stochastic solution of Schrödinger's equation. Using ground-state QMC plus phonons within the quasiharmonic approximation of density functional perturbation theory, we obtain the thermal pressure and equations of state of silica phases up to Earth's core-mantle boundary. Our results provide the best constrained equations of state and phase boundaries available for silica. QMC indicates a transition to the dense α-PbO 2 structure above the core-insulating D" layer, but the absence of a seismic signature suggests the transition does not contribute significantly to global seismic discontinuities in the lower mantle. However, the transition could still provide seismic signals from deeply subducted oceanic crust. We also find an accurate shear elastic constant for stishovite and its geophysically important softening with pressure.first principles computations | lower mantle | thermal properties Introduction Silica is one of the most widely studied materials across the fields of materials science, physics, and geology. It plays important roles in many applications, including ceramics, electronics, and glass production. As the simplest of the silicates, silica is also one of the most ubiquitous geophysically important minerals. It can exist as a free phase in some portions of the Earth's mantle. In order to better understand geophysical roles silica plays in Earth, much focus is placed on improving knowledge of fundamental silica properties. Studying structural and chemical properties (1) offers insight into the bonding and electronic structure of silica and provides a realistic testbed for theoretical method development. Furthermore, studies of free silica under compression (2-7) reveal a rich variety of structures and properties, which are prototypical for the behavior of Earth minerals from the surface through the crust and mantle. However, the abundance of free silica phases and their role in the structure and dynamics of deep Earth is still unknown.Free silica phases may form in the Earth as part of subducted slabs (8) or due to chemical reactions with molten iron (9). Determination of the phase stability fields and thermodynamic equations of state are crucial to understand the role of silica in Earth. The ambient phase, quartz, is a fourfold coordinated, hexagonal struc...

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Section: Introductionmentioning

confidence: 69%

Quantum Monte Carlo computations of phase stability, equations of state, and elasticity of high-pressure silica

Driver

Cohen

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…These oxides are a major constituent of the earth's lower mantle (between 600 and 2900 km in depth). The electronic structure [2,3], structural phase transitions [2][3][4][5], elasticity [4][5][6][7][8], thermal properties [9], stability and the equation of state [10,11] of these oxides have been extensively studied theoretically and experimentally [1,[23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Elastic properties of alkaline earth oxides under high pressure

Singh

Gupta

Goyal

2007

Physica B: Condensed Matter

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“…This cutoff is very large by the normal standards of DFT calculations, but there is evidence that using large basis sets reduces the variance of the energy in QMC calculations. 10 B. QMC calculations…”

Section: Dft Orbital-generation Calculationsmentioning

confidence: 99%

Quantum Monte Carlo, density functional theory, and pair potential studies of solid neon

Drummond

Needs

2006

Phys. Rev. B

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We report quantum Monte Carlo (QMC), plane-wave density-functional theory (DFT), and interatomic pair-potential calculations of the zero-temperature equation of state (EOS) of solid neon. We find that the DFT EOS depends strongly on the choice of exchange-correlation functional, whereas the QMC EOS is extremely close to both the experimental EOS and the EOS obtained using the best semiempirical pair potential in the literature. This suggests that QMC is able to give an accurate treatment of van der Waals forces in real materials, unlike DFT. We calculate the QMC EOS up to very high densities, beyond the range of values for which experimental data are currently available. At high densities the QMC EOS is more accurate than the pair-potential EOS. We generate a different pair potential for neon by a direct evaluation of the QMC energy as a function of the separation of an isolated pair of neon atoms. The resulting pair potential reproduces the EOS more accurately than the equivalent potential generated using the coupled-cluster CCSD(T) method.

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Quantum Monte Carlo calculations of the structural properties and the B1-B2 phase transition of MgO

Cited by 61 publications

References 49 publications

Quantum Monte Carlo computations of phase stability, equations of state, and elasticity of high-pressure silica

Quantum Monte Carlo computations of phase stability, equations of state, and elasticity of high-pressure silica

Elastic properties of alkaline earth oxides under high pressure

Quantum Monte Carlo, density functional theory, and pair potential studies of solid neon

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