Ab initio total energy study of brucite, diaspore and hypothetical hydrous wadsleyite

Winkler, Bjoern; Milman, Victor; Hennion, B.; Payne, Mike C.; Lee, M. H.; Lin, Jingxiang

doi:10.1007/bf00200324

Cited by 43 publications

(35 citation statements)

References 29 publications

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“…Early studies on bulk AEMHs revealed that the application of temperature and pressure may result in dramatical changes in their crystal structure and their electronic properties [11][12][13][14][15][16][17][18]. Moreover, early theoretical studies showed the reliability of the use of first principles calculations with a plane-wave basis set in combination with the generalized gradient approximation exchange-correlation functional for the investigation of structural and electronic properties of these materials [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Portlandite crystal: Bulk, bilayer, and monolayer structures

et al. 2015

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Ca(OH) 2 crystals, well known as portlandite, are grown in layered form, and we found that they can be exfoliated on different substrates. We performed first principles calculations to investigate the structural, electronic, vibrational, and mechanical properties of bulk, bilayer, and monolayer structures of this material. Different from other lamellar structures such as graphite and transition-metal dichalcogenides, intralayer bonding in Ca(OH) 2 is mainly ionic, while the interlayer interaction remains a weak dispersion-type force. Unlike well-known transition-metal dichalcogenides that exhibit an indirect-to-direct band gap crossover when going from bulk to a single layer, Ca(OH) 2 is a direct band gap semiconductor independent of the number layers. The in-plane Young's modulus and the in-plane shear modulus of monolayer Ca(OH) 2 are predicted to be quite low while the in-plane Poisson ratio is larger in comparison to those in the monolayer of ionic crystal BN. We measured the Raman spectrum of bulk Ca(OH) 2 and identified the high-frequency OH stretching mode A 1g at 3620 cm −1 . In this study, bilayer and monolayer portlandite [Ca(OH) 2 ] are predicted to be stable and their characteristics are analyzed in detail. Our results can guide further research on ultrathin hydroxites.

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Section: Introductionmentioning

confidence: 99%

Portlandite crystal: Bulk, bilayer, and monolayer structures

et al. 2015

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“…From the theoretical side, in the focus were mainly structural, vibrational and chemical properties. 32,33 Recent studies on the electronic structure were undertaken primarily to understand novel opto-electronic properties of Mg(OH) 2 :C films.…”

Section: Introductionmentioning

confidence: 99%

Materials properties of magnesium and calcium hydroxides from first-principles calculations

Pishtshev

Karazhanov

Klopov

2014

Computational Materials Science

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This work presents a study of ground state properties, electronic structure, dielectric and optical properties of magnesium and calcium hydroxides X(OH)2 (X = Mg and Ca) within PBE-GGA and range-separated hybrid functional schemes as well as by using GW approximation. The relevant HSE06 hybrid functional mixing parameters were determined from a self-consistent adjustment to the electronic dielectric constant ǫ∞. It was shown that the overall performance of our adaptation of the HSE06 functional via implementation of the modified amount of the Fock exchange is nearly best for the ground state properties as compared to other relevant HF and DFT methods. Structural stability of the crystalline X(OH)2 hydroxides has been considered in static and dynamic aspects. The most important factors describing the bonding situation have been investigated, and a crystalchemical integrity of the hydroxides has been analyzed. From electronic structure studies it was found that both materials are direct band gap insulators. Predictions for the fundamental band gaps were shown to be in the range of 7.7-8.3 eV for Mg(OH) 2 and 7.3-7.6 eV for Ca(OH) 2 . The origin of the conduction and valence band states near the band edges has been studied in terms of orbital and site projected density of states as well as by comparison with the X-ray photoelectron spectroscopy measurements. It was shown that effective masses of carriers at the Γ-point in vicinity of the band extreme are strongly anisotropic and for the electrons are similar to those in the ZnO crystal. Optical properties of the bulk X(OH)2 hydroxides have been investigated in terms of the real and imaginary parts of the optical dielectric function calculated in GW approximation. Electronic character of anisotropy of optical properties has been clarified. On the base of the obtained results the potential of applicability of the Mg(OH) 2 and Ca(OH) 2 crystalline hydroxides in semiconductor device engineering and optoelectronics has been analyzed.

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“…Then, he proposed a hypothetical structure of hydrous wadsleyite [Smyth, 1994]. The proposed defect structure was studied by quantum mechanical simulations [Winkler et al, 1995]. The stability of protonated O1 site in wadsleyite was confirmed by ab initio molecular dynamics [Haiber et al, 1997] and interatomic model potential calculations [Walker et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

Tsuchiya

2009

J. Geophys. Res.

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Protons are found to bond to the O1 site to align the OH dipoles along the edges of M3 vacancies. Calculated elastic constants, bulk and shear moduli, are found to decrease almost linearly with increasing water content but to increase linearly with increasing pressure. At 15 GPa and static 0 K condition, incorporation of 3.3 wt % H 2 O into wadsleyite, which corresponds to the maximum solubility of hydrous wadsleyite, reduces V P and V S by about 3.9 and 4.8%, respectively. This indicates that 1 wt % H 2 O hydration of wadsleyite corresponds to the temperature effects on bulk and shear moduli about 430 K (0 GPa) to 340 K (20 GPa) and 350 K (0 GPa) to 290 K (20 GPa), respectively. The transversely isotropic aggregates demonstrate largest positive polarization anisotropy V SH À V SV when the c axis aligns vertically in both dry and wet cases.Citation: Tsuchiya, J., and T. Tsuchiya (2009), First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure,

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Ab initio total energy study of brucite, diaspore and hypothetical hydrous wadsleyite

Cited by 43 publications

References 29 publications

Portlandite crystal: Bulk, bilayer, and monolayer structures

Portlandite crystal: Bulk, bilayer, and monolayer structures

Materials properties of magnesium and calcium hydroxides from first-principles calculations

First principles investigation of the structural and elastic properties of hydrous wadsleyite under pressure

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