scispace - formally typeset
Search or ask a question
Author

I. Bernal

Bio: I. Bernal is an academic researcher from University of Houston. The author has contributed to research in topics: Crystal structure & Lattice constant. The author has an hindex of 1, co-authored 1 publications receiving 39 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the cubic form of indium trihydroxide was obtained by hydrothermal methods at varied concentrations and temperatures. But the final refinement based on 106 independent reflections yields a conventional R value of 1.48%.

41 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors derived a hierarchy of hettotype structures which are derivatives of the arisotypic cubic perovskite structure (ABX 3 ), exemplified by SrTiO 3 (tausonite) or KMgF 3 (parascandolaite) by tilting and distortion of the BX 6 octahedra.
Abstract: On the basis of extensive studies of synthetic perovskite-structured compounds it is possible to derive a hierarchy of hettotype structures which are derivatives of the arisotypic cubic perovskite structure ( ABX 3 ), exemplified by SrTiO 3 (tausonite) or KMgF 3 (parascandolaite) by: (1) tilting and distortion of the BX 6 octahedra; (2) ordering of A- and B -site cations; (3) formation of A -, B - or X -site vacancies. This hierarchical scheme can be applied to some naturally-occurring oxides, fluorides, hydroxides, chlorides, arsenides, intermetallic compounds and silicates which adopt such derivative crystal structures. Application of this hierarchical scheme to naturally-occurring minerals results in the recognition of a perovskite supergroup which is divided into stoichiometric and non-stoichiometric perovskite groups, with both groups further divided into single ABX 3 or double A 2 BB ʹ X 6 perovskites. Subgroups, and potential subgroups, of stoichiometric perovskites include: (1) silicate single perovskites of the bridgmanite subgroup; (2) oxide single perovskites of the perovskite subgroup (tausonite, perovskite, loparite, lueshite, isolueshite, lakargiite, megawite); (3) oxide single perovskites of the macedonite subgroup which exhibit second order Jahn-Teller distortions (macedonite, barioperovskite); (4) fluoride single perovskites of the neighborite subgroup (neighborite, parascandolaite); (5) chloride single perovskites of the chlorocalcite subgroup; (6) B- site cation ordered double fluoride perovskites of the cryolite subgroup (cryolite, elpasolite, simmonsite); (7) B- site cation ordered oxide double perovskites of the vapnikite subgroup [vapnikite, (?) latrappite]. Non-stoichiometric perovskites include: (1) A- site vacant double hydroxides, or hydroxide perovskites, belonging to the sohngeite, schoenfliesite and stottite subgroups; (2) Anion-deficient perovskites of the brownmillerite subgroup (srebrodolskite, shulamitite); (3) A- site vacant quadruple perovskites (skutterudite subgroup); (4) B -site vacant single perovskites of the oskarssonite subgroup [oskarssonite]; (5) B -site vacant inverse single perovskites of the cohenite and auricupride subgroups; (6) B -site vacant double perovskites of the diaboleite subgroup; (7) anion-deficient partly-inverse B -site quadruple perovskites of the hematophanite subgroup.

89 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present updated correlations between 1 H chemical shift and O ··· O and H ··· o distances of O-H · − O hydrogen bonds, derived from a comprehensive 1H chemical shift database containing both original high-quality fast magic angle spinning (MAS) and two-dimensional combined rotation and multiple pulse spectroscopy (CRAMPS)-MAS NMR data and literature MAS NMRI data for a large number of inorganic compounds, including phosphates, silicates, (oxy)hydroxides, borates, sulfates, and
Abstract: Solid-state 1 H nuclear magnetic resonance (NMR) spectroscopy has developed into a versatile, high-resolution method for elucidating the detailed structures of both crystalline and amorphous materials. Here, we summarize our recent endeavors in applying this method to crystalline and glassy silicates and related inorganic materials. We first present updated correlations between 1 H chemical shift and O ··· O and H ··· O distances of O-H ··· O hydrogen bonds, derived from a comprehensive 1 H chemical shift database containing both original high-quality fast magic angle spinning (MAS) and two-dimensional combined rotation and multiple pulse spectroscopy (CRAMPS)-MAS NMR data and literature MAS NMR data for a large number of inorganic compounds, including phosphates, silicates, (oxy)hydroxides, borates, sulfates, and carbonates. These correlations may be used to estimate hydrogen-bonding distances for inorganic oxide materials of unknown structures. We then present case studies for the application of high-resolution two-dimensional 1 H CRAMPS-MAS NMR to unravel the order/disorder of proton distributions in crystalline high-pressure hydrous silicates. Finally, we summarize some of our results on the water speciation in hydrous (alumino)silicate glasses of a range of compositions obtained through comprehensive 1 H MAS NMR, and 29 Si- 1 H and 27 Al- 1 H double-resonance NMR experiments, and analyze them in the framework of a quasi-chemical model.

82 citations

Journal ArticleDOI
TL;DR: In this paper, the thermodynamic stability of four experimentally observed low-index surfaces of bcc indium oxide (In{}_{2}$O${}_{3}$) is investigated by means of density functional theory calculations.
Abstract: The thermodynamic stability of four experimentally observed low-index surfaces of bcc indium oxide (In${}_{2}$O${}_{3}$) is investigated by means of density functional theory calculations. The influence of the environment is studied as well as the influence of hydrogen and water. We find that $(001)$ surfaces exhibit the most complex reconstructions. The influence $n$-type dopants (Sn), as well as the in-plane lattice strain is studied for the $(001)$ orientation. Finally, scanning tunneling microscopy images are presented and discussed in light of recent experiments.

79 citations

Journal ArticleDOI
TL;DR: In order to shed light on the proton distributions and order/disorder in high-pressure delta-Al(OH)3 and delta-alOOH phases, two-dimensional, high-resolution 1H CRAMPS (FSLG)-MAS NMR and 27Al 3QMAS NMRI spectra have been obtained as mentioned in this paper.
Abstract: In order to shed light on the proton distributions and order/disorder in high-pressure delta-Al(OH)3 and delta-AlOOH phases, two-dimensional, high-resolution 1H CRAMPS (FSLG)-MAS NMR and 27Al 3QMAS NMR spectra have been obtained. For delta-Al(OH)3, the 1H CRAMPS-MAS NMR revealed two peaks with an intensity ratio close to 2:1. The 27Al MAS and 3QMAS NMR suggest a single Al site with a well-defined local structure. For delta-AlOOH, the 1H and 27Al NMR indicate the presence of a single H and Al site each. These results are consistent with crystal structures refined from X-ray diffraction. For comparison, 1H MAS and CRAMPS-MAS NMR spectra were also obtained for several other hydroxides/oxyhydroxides, including In(OH)3 and InOOH that have similar structures to delta-Al(OH)3 and delta-AlOOH, respectively. These data not only provide additional insights into the proton distributions in these important crystal structure classes but also together provide a better defined quantitative correlation between 1H chemical shift and hydrogen-bonding O...O distance.

71 citations