29Si AND 23Na MAS NMR SPECTROSCOPIC STUDY OF THE POLYTYPES OF THE TITANOSILICATE PENKVILKSITE

Sherriff, Barbara L.; Zhou, Bing

doi:10.2113/gscanmin.42.4.1027

Cited by 12 publications

(2 citation statements)

References 21 publications

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“…10,6 For example, Full Potential Linear Augmented Plane Wave (FP LAPW) modeling has been widely used for theoretical calculations and the prediction of electronic and other properties, including EFG, for solids with periodic boundary conditions. [11][12][13][14][15][16][17] For this full-potential and all-electron method, the electronic potential in the unit cell is partitioned into non-overlapping atom-centered spheres and an interstitial area between the spheres (Muffin-Tin partition), no approximation to either the potential or charge density is made, and the exchange and correlation effects are treated in the density functional theory (DFT) using the generalized gradient approximation (GGA). A linear combination of the products of radial functions and spherical harmonics is then used inside the atomic spheres and a plane wave expansion is used in the interstitial area as the basis sets.…”

Section: Introductionmentioning

confidence: 99%

11B and 23Na solid-state NMR and density functional theory studies of electric field gradients at boron sites in ulexite

et al. 2013

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Nuclear magnetic resonance (NMR) parameters of 11 B in borates and borosilicates, unlike those of many other nuclei such as 29 Si and 27 Al, vary only over limited ranges and have been thought to be insensitive to local structural environments. High-resolution NMR spectroscopy at high (14 T) and ultrahigh (21 T) fields yield precise 11 B and 23 Na NMR parameters for ulexite, which contains the pentaborate polyanion ([B 5 O 6 (OH) 6 ] 3−) as the fundamental building block (FBB). These NMR parameters are compared with ab initio theoretical calculations as implemented in WIEN2K, including optimization of the ulexite structure, determination of the electric field gradients (EFG) and consequently the nuclear quadrupole interaction (QI) parameters at the five distinct B sites, and calculations of the density of states (DOS). These calculations show that the magnitudes and signs of the EFG for [3] B and [4] B are determined by multiple factors, including the electron distributions in the B 2p z orbitals and their interactions with Ca-3p/O-2s orbitals. Most importantly, the calculated B 2p z orbitals at all B sites in ulexite are predominantly affected by the atoms within the fundamental building block, resulting in the insensitivity of the 11 B QI parameters to the weak interunit interactions among FBB. Calculations with the water molecules removed from the ulexite structure provide further support for the strong intraunit interactions in FBB as a cause for the poor sensitivity of 11 B NMR parameters to local structural environments, including hydrogen bonding, in borates.

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Section: Introductionmentioning

confidence: 99%

11B and 23Na solid-state NMR and density functional theory studies of electric field gradients at boron sites in ulexite

et al. 2013

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“…137 The phase composition of Na 4 Ti 2 Si 8 O 22 Á 5H 2 O was established by 23 Na and 29 Si MAS NMR spectra. 138 The structure of T 8 O 10 (citrate) 4 (H 2 O) 12 was established by 13 C CP/MAS NMR. 139 29 Si NMR spectra of polymetallasiloxanes (M = Ti or Zr) were used in structural characterisation.…”

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confidence: 99%

Solid state NMR spectroscopy

Davidson¹

Spectroscopic Properties of Inorganic and Organometallic Compounds

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Correlations between 11B NMR parameters and structural characters in borate and borosilicate minerals investigated by high-resolution MAS NMR and ab initio calculations

Zhou

Sun

Yao³

et al. 2012

Phys Chem Minerals

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Borates consisting of diverse fundamental building blocks (FBB) formed from complex polymerization of planar triangular [B/ 3 ] groups and tetrahedral [B/ 4 ] groups, where / = O and OH, provide an excellent opportunity for investigation of correlations between the NMR parameters and local structures. However, previous studies suggested that the 11 B NMR parameters in borates are insensitive to local structural environments other than the B coordination number, in contrast to those documented for 29 Si, 23 Na and 27 Al in silicates, and no correlation between 11 B chemical shifts and the sum of bond valences has been established for borate minerals with hydroxyl groups or molecular water in the structures. In this study, high-resolution NMR spectra have been acquired at the ultra high field of 21 T as well as at 14 T for selected borate and borosilicate minerals, and have been used to extract high-precision NMR parameters by using combined ab initio theoretical calculations and spectral simulations. These new NMR parameters reveal subtle correlations with various structural characters, especially the effects of the 11 B chemical shifts from the bridging oxygen atom(s), site symmetry, symmetry of FBB, the sum of bond valences, as well as the next-nearest-neighbor cations and hydrogen bonding. Also, these results provide new insights into the shielding mechanism for 11 B in borate and borosilicate minerals. In particular, this study demonstrates that the small variation in 11 B chemical shifts can still be used to probe the local structural environments and that the established correlations can be used to investigate the structural details in borates and amorphous materials.

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29Si AND 23Na MAS NMR SPECTROSCOPIC STUDY OF THE POLYTYPES OF THE TITANOSILICATE PENKVILKSITE

Cited by 12 publications

References 21 publications

11B and 23Na solid-state NMR and density functional theory studies of electric field gradients at boron sites in ulexite

11B and 23Na solid-state NMR and density functional theory studies of electric field gradients at boron sites in ulexite

Solid state NMR spectroscopy

Correlations between 11B NMR parameters and structural characters in borate and borosilicate minerals investigated by high-resolution MAS NMR and ab initio calculations

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