A New Polytype of Orthoboric Acid, H<sub>3</sub>BO<sub>3</sub>‐3T.

Shuvalov, Robert R.; Burns, Peter C.

doi:10.1002/chin.200339006

Cited by 4 publications

(9 citation statements)

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“…For the isolated boric acid molecule, the normal modes below 1000 cm –1 are shifted downward in comparison to those of the crystal and have fewer features in common with the latter (only four maxima can be discerned, while the theoretical curves exhibit five). Overall, the data we present are in agreement with other experimental reports − (see Table ) and surpass the quality of estimates which were performed using a more accurate exchange-correlation functional but without van der Waals corrections. , …”

Section: Resultssupporting

confidence: 92%

“…Table 1 depicts the calculated a, b, and c lattice parameters, the α, β, and γ unit cell angles, and the interplanar distance d for the boric acid H 3 BO 3 -2A and H 3 BO 3 -3T levels of calculation. The experimental data of Zachariasen 9 and Shuvalov et al 37 are shown for the sake of comparison. One can observe that computations at the LDA level predict lattice parameters for H 3 BO 3 -2A that are significantly smaller than the X-ray diffraction data.…”

Section: Resultsmentioning

confidence: 99%

“…The H 3 BO 3 -2A structure has a primitive triclinic unit cell with space group symmetry P1¯being formed by stacked H 3 BO 3 displaced planes in the repeating sequence AB..., 10 which are 3.18 Å apart as shown in Figure 1a. The H 3 BO 3 -3T polymorph is trigonal and has P3 2 symmetry, being formed by stacked displaced planes in the repeating sequence ABC... 37 with an interplanar distance of 3.19 Å (see Figure 1b). The atom labels used in this work are also depicted in Figure 1a−c.…”

Section: Methodsmentioning

confidence: 99%

“…Each sheet is formed by H 3 BO 3 molecular units with nearly perfect C 3h symmetry, linked together through hydrogen bonds. Later, the exploratory research on boron synthetic compounds by Shuvalov and Burns 11 indicated the crystallographic structure of a new trigonal polytype of boric acid, H 3 BO 3 -3T, with triple-layer sheets stacked in the repeating sequence pattern ABC.... Therefore, the two crystalline layered boric acid polymorphs were labeled as H 3 BO 3 -2A (double layer) and H 3 BO 3 -3T (triple layer).…”

Section: Introductionmentioning

confidence: 99%

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Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations

et al. 2018

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Boric acid (HBO) is being used effectively nowadays in traps/baits for the management of Aedes aegypti L. and Aedes albopictus Skuse species of mosquitoes, which are the main spreading vectors worldwide for diseases such as malaria, dengue, and zika. Previously, we published results on the structural, electronic, and optical properties of its molecular triclinic HBO-2A and trigonal HBO-3T polymorphs within the framework of density functional theory (DFT). Because of the renewed importance of these materials, the focus of this work is on the vibrational properties of the bulk boric acid 2A and 3T polymorphs. We measured the infrared and Raman spectra of the former, which was accompanied and interpreted through state-of-the-art DFT calculations, supplemented by computations regarding the HBO molecule and two-dimensional layers based on the bulk structures. We identify/assign their normal modes and find vibrational signatures for each polymorph as well as in- and out-of-plane motions and molecular vibrations, unveiling a nice agreement between the DFT level of theory employed and our improved spectroscopic measurements in the wavenumber ranges of 400-2000 cm (infrared) and 0-1500 cm (Raman). We show that a dispersion-corrected DFT functional within the generalized gradient approximation (GGA) can be very accurate in describing the vibrational properties of the boric acid polymorphs. Besides, several issues left open/not clearly resolved in previously published works on the vibrational mode assignments of the bulk and 2D sheets of boric acid are explained satisfactorily. Finally, phonon dispersions and associated densities of states were also evaluated for each polymorph along with their temperature-dependent DFT-calculated entropy, enthalpy, free energy, heat capacity, and Debye temperature. In particular, our DFT calculations suggest a possible way to differentiate the 2A and 3T boric acid polymorphs through Raman spectroscopy and heat capacity measurements.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations

et al. 2018

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“…Although the crystal system is reported in the literature to be triclinic for the orthoboric acid [22], the crystal habit (characteristic external shape of an individual crystal or crystal group) for the mineral develops pseudo-hexagonal crystals due to cyclic twinning-similar to aragonite [23]. The boric acid has also a trigonal polytype of orthoboric acid [22,24], while the metaboric acid has three polytypes: orthorhombic [25], monoclinic [26] and cubic [27], each one with its characteristic melting point.…”

Section: Introductionmentioning

confidence: 96%

Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow

Rotaru

2016

J Therm Anal Calorim

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Boric acid is a very important inorganic material with diverse uses in optoelectronics, petroleum industry, medicine, agriculture, etc. Recently, it was reported on the modification of the crystallization system of the triclinic boric acid (TBA) to hexagonal boric acid (HBA), when a special obtaining procedure is applied. In this paper, the thermokinetic stability of HBA novel material was comparatively studied with respect to the well-known TBA, in air flow atmosphere. Both HBA and TBA undergo a threestep overall thermal decomposition reaction (dehydration), following similar pathways; from the thermodynamic point of view HBA is more stable-decomposition temperatures and DH are higher in this case compared to those of TBA. The kinetic analysis was performed by means of the isoconversional methods, for each step of dehydration observing different thermokinetic regions. Higher thermal stability for HBA enables it to be employed at higher temperatures instead of TBA, explaining why the triclinic symmetry enhances the formation actually of the pseudohexagonal crystals as crystal habit at the macroscopic scale. Lower thermodynamic and kinetic stability of HBA makes it easier to be activated and thus more instable at the microstructural scale: this is an indirect proof of the TBA presence in the usual surrounding conditions and in the same time raises the probability for HBA molecules to slide onto their crystalline layers due to the lability of hydrogen bonds keeping them and thus increased potential to intercalate with other molecules. The present results open the possibility for promising applications of HBA as a better lubricant for various industries, while in the medical sector superior cleanser, antifungal and antibacterial properties may be foreseen.

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Structural, Electronic, and Optical Properties of Bulk Boric Acid2Aand3TPolymorphs: Experiment and Density Functional Theory Calculations

Silva

Santos

Cunha

et al. 2016

Crystal Growth & Design

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Boric acid (H3BO3) is being used effectively nowadays in traps/baits for the management of Aedes aegypti L. and Aedes albopictus Skuse species of mosquitos, which are the main spreading vectors for diseases like malaria, dengue, and zika worldwide. Due to its renewed importance, we have studied in this work the structural, electronic, and optical properties of its molecular triclinic H3BO3-2A and trigonal H3BO3-3T polymorphs within the framework of density functional theory (DFT) at the local density and generalized gradient levels of calculations, LDA and GGA, respectively, improving and extending previously published theoretical results on triclinic boric acid structural properties. In addition, the optical absorption of the 2A polymorph was measured in this work for the sake of comparison with our DFT estimate. In comparison to published X-ray diffraction data, unit cell deviations as small as Δa ∼ −0.13 Å (−0.12 Å), Δb ∼ −0.13 Å (−0.12 Å), Δc ∼ 0.18 Å (−0.31 Å), and interplanar distance deviation Δd ∼ −0.11 Å (−0.10 Å) for H3BO3-2A (H3BO3-3T) were obtained using a Tkatchenko and Scheffler dispersion corrected GGA functional. The properties of the polymorphs are shown to be ruled by an interplay between in-plane hydrogen bonds and interplanar van der Waals interactions. However, the molecular stacking pattern, AB for H3BO3-2A and ABC for H3BO3-3T, does not lead to significantly distinct electronic and optical properties. Both polymorphs are suggested to be insulators with indirect bang gaps of about 6.26 ± 0.01 eV, which is in close agreement with the 5.98 eV indirect band gap we have measured for triclinic boric acid by optical absorption. Notably the usual DFT gap underestimation is not observed due to the extra shrinking of the unit cell caused by the inclusion of van der Waals forces in the geometry optimization. The complex dielectric function and optical absorption of both boric acid polymorphs were characterized as well.

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A New Polytype of Orthoboric Acid, H₃BO₃‐3T.

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 4 publications

References 1 publication

Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations

Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations

Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow

Structural, Electronic, and Optical Properties of Bulk Boric Acid2Aand3TPolymorphs: Experiment and Density Functional Theory Calculations

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A New Polytype of Orthoboric Acid, H3BO3‐3T.

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 4 publications

References 1 publication

Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations

Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations

Thermal and kinetic study of hexagonal boric acid versus triclinic boric acid in air flow

Structural, Electronic, and Optical Properties of Bulk Boric Acid2Aand3TPolymorphs: Experiment and Density Functional Theory Calculations

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Product

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A New Polytype of Orthoboric Acid, H₃BO₃‐3T.