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Majhi, D., Stevensson, B., Nguyen, T. T. & Edén, M. (2024). 1H and 13C chemical shift-structure effects in anhydrous β-caffeine and four caffeine-diacid cocrystals probed by solid-state NMR experiments and DFT calculations. Physical Chemistry, Chemical Physics - PCCP
Open this publication in new window or tab >>1H and 13C chemical shift-structure effects in anhydrous β-caffeine and four caffeine-diacid cocrystals probed by solid-state NMR experiments and DFT calculations
2024 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Refereed) Epub ahead of print
Abstract [en]

By using density functional theory (DFT) calculations, we refined the H atom positions in the structures of β-caffeine (C), α-oxalic acid (OA; (COOH)2), α-(COOH)2·2H2O, β-malonic acid (MA), β-glutaric acid (GA), and I-maleic acid (ME), along with their corresponding cocrystals of 2 : 1 (2C–OA, 2C–MA) or 1 : 1 (C–GA, C–ME) stoichiometry. The corresponding 13C/1H chemical shifts obtained by gauge including projector augmented wave (GIPAW) calculations agreed overall very well with results from magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy experiments. Chemical-shift/structure trends of the precursors and cocrystals were examined, where good linear correlations resulted for all COO1H sites against the H⋯O and/or H⋯N H-bond distance, whereas a general correlation was neither found for the aliphatic/caffeine-stemming 1H sites nor any 13C chemical shift against either the intermolecular hydrogen- or tetrel-bond distance, except for the 13COOH sites of the 2C–OA, 2C–MA, and C–GA cocrystals, which are involved in a strong COOHN bond with caffeine that is responsible for the main supramolecular stabilization of the cocrystal. We provide the first complete 13C NMR spectral assignment of the structurally disordered anhydrous β-caffeine polymorph. The results are discussed in relation to previous literature on the disordered α-caffeine polymorph and the ordered hydrated counterpart, along with recommendations for NMR experimentation that will secure sufficient 13C signal-resolution for reliable resonance/site assignments.

National Category
Theoretical Chemistry Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-229374 (URN)10.1039/d3cp06197c (DOI)001217081300001 ()38700003 (PubMedID)
Available from: 2024-05-22 Created: 2024-05-22 Last updated: 2024-05-27
Lv, P., Stevensson, B., Yu, Y., Wang, T. & Edén, M. (2023). BO3/BO4 Intermixing in Borosilicate Glass Networks Probed by Double-Quantum 11B NMR: What Factors Govern BO4-BO4 Formation?. The Journal of Physical Chemistry C, 127(40), 20026-20040
Open this publication in new window or tab >>BO3/BO4 Intermixing in Borosilicate Glass Networks Probed by Double-Quantum 11B NMR: What Factors Govern BO4-BO4 Formation?
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2023 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 40, p. 20026-20040Article in journal (Refereed) Published
Abstract [en]

We examine the borate group intermixing in a series of 25 borosilicate (BS) glasses from the [0.5M(2)O–0.5Na2O]–B2O3–SiO2 systems with M = {Li, K, Rb, Mg, Ca} along with ternary K2O–B2O3–SiO2 and Na2O–B2O3–SiO2 glasses by double-quantum–single-quantum (2Q–1Q) 11B correlation nuclear magnetic resonance (NMR) experiments. The alterations of the fractional populations of B[3]–O–B[3], B[3]–O–B[4], and B[4]–O–B[4] linkages in the glass networks were monitored for variable nSi/nB molar ratios, nonbridging O contents of the glass, and the (average) cation field strength (CFS) of the Mz+/Na+ network modifiers. A significant B[4]–O–B[4] bonding is observed in all glasses, thereby conclusively demonstrating that the normally assumed “BO4–BO4 avoidance” is far from strict in BS glasses, regardless of the Mz+ field strength. We show that the degree of B[4]–O–B[4] bonding depends foremost on its underlying BO4 population and to a lesser degree on the NBO content of the glass; we also provide a straightforward prediction of the B[4]–O–B[4] population in an arbitrary BS glass from parameters readily obtained by routine 11B NMR. The propensity for forming B[4]–O–B[4] linkages increases concurrently with either the CFS or the amount of glass network modifiers, roughly scaling as the square root of the “effective CFS” that encompasses both parameters. Although BO3–BO3 and BO3–BO4 pairs remain favored throughout all examined BS glass networks, the borate group intermixing randomizes significantly for increasing effective CFS, out of which the amount and charge of the glass-network modifier cations dominate over their size. Our results are discussed in relation to the two prevailing but formally mutually exclusive “random network” and “superstructural unit” models of borate and BS glasses.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-223938 (URN)10.1021/acs.jpcc.3c03577 (DOI)001077652100001 ()2-s2.0-85176126762 (Scopus ID)
Available from: 2023-11-27 Created: 2023-11-27 Last updated: 2024-01-11Bibliographically approved
Lv, Z.-P., Sun, Z., Wang, F., Yu, Y., Yang, F., Yue, S., . . . Wang, T. (2023). Cation field-strength effects on ion irradiation-induced mechanical property changes of borosilicate glass structures. Journal of The American Ceramic Society, 106(10), 5766-5780
Open this publication in new window or tab >>Cation field-strength effects on ion irradiation-induced mechanical property changes of borosilicate glass structures
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2023 (English)In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 106, no 10, p. 5766-5780Article in journal (Refereed) Published
Abstract [en]

We examine the impact of the glass network-modifier cation field strength (CFS) on ion irradiation-induced mechanical property changes in borosilicate (BS) glasses for the ternary M2O-B2O3-SiO2 systems with M = {Na, K, Rb} and the quaternary [0.5M((2))O-0.5Na(2)O]-B2O3-SiO2 systems with M = {Li, Na, K, Rb Mg, Ca, Sr, Ba}. B-11 nuclear magnetic resonance (NMR) experiments on the as-prepared BS glasses yielded the fractional population of four-coordinated B species (B-[4]) out of all {B-[3], B-[4]} groups in the glass network, along with the fraction of B-[4]-O-Si linkages out of all B-[4]-O-Si/B bonds. Both parameters correlated linearly with the (average) CFS of the M+ and/or {M(2)+, Na+} cations. Both the nanoindentation-derived hardness and Young's modulus values of the glasses reduced upon their irradiation by Si2+ ions, with the property deterioration decreasing linearly with increasing Mz+ CFS, that is, for higher Mz+center dot center dot center dot O interaction strength. The irradiation damage of the glass network also increased linearly with the fraction of B-[4]-O-Si linkages, which are the second weakest in the structure after the Mz+center dot center dot center dot O bonds. Our results underscore the advantages of employing BS glasses with high-CFS cations for enhancing the radiation resistance for nuclear waste storage.

Keywords
B-11 MAS NMR, borosilicate glass, composition-structure-property correlations, ion irradiation, mechanical properties
National Category
Materials Engineering
Identifiers
urn:nbn:se:su:diva-221323 (URN)10.1111/jace.19213 (DOI)001016060400001 ()2-s2.0-85162892898 (Scopus ID)
Available from: 2023-09-19 Created: 2023-09-19 Last updated: 2023-09-19Bibliographically approved
Ali, S., Ellison, A., Luo, J. & Edén, M. (2023). Composition-structure-property relationships of transparent Ca-Al-Si-O-N oxynitride glasses: The roles of nitrogen and aluminum. Journal of The American Ceramic Society, 106(3), 1748-1765
Open this publication in new window or tab >>Composition-structure-property relationships of transparent Ca-Al-Si-O-N oxynitride glasses: The roles of nitrogen and aluminum
2023 (English)In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 106, no 3, p. 1748-1765Article in journal (Refereed) Published
Abstract [en]

We explore the formation and composition–structure–property correlations of transparent Ca–Al–Si–O–N glasses, which were prepared by a standard melt-quenching technique using AlN as the nitrogen source and incorporating up to 8 at.% of N. Their measured physical properties of density, molar volume, compactness, refractive index, and hardness—along with the Young, shear, and bulk elastic moduli—depended roughly linearly on the N content. These effects are attributed primarily to the improved glass-network cross-linking from N compared to O, rather than the formation of higher-coordination AlO5 and AlO6 groups, where 27Al magic-angle-spinning nuclear magnetic resonance experimentation revealed that aluminum is predominately present in tetrahedral coordination as AlO4 units. Yet, several physical properties, such as the refractive index along with the bulk, shear, and Young's elastic moduli, increase concomitantly with the Al content of the glass. We discuss the incompletely understood mechanical–property boosting role of Al as observed both herein and in previous reports on oxynitride glasses, moreover suggesting glass-composition domains that are likely to offer optimal mechanical properties. 

Keywords
Al-27 nuclear magnetic resonance, elastic properties, glass structure, hardness, Loewenstein Al avoidance
National Category
Materials Engineering
Identifiers
urn:nbn:se:su:diva-211535 (URN)10.1111/jace.18866 (DOI)000881945600001 ()2-s2.0-85142015820 (Scopus ID)
Available from: 2022-11-23 Created: 2022-11-23 Last updated: 2023-01-02Bibliographically approved
Stevensson, B. & Edén, M. (2023). Improved reweighting protocols for variationally enhanced sampling simulations with multiple walkers. Physical Chemistry, Chemical Physics - PCCP, 25(33), 22063-22078
Open this publication in new window or tab >>Improved reweighting protocols for variationally enhanced sampling simulations with multiple walkers
2023 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, no 33, p. 22063-22078Article in journal (Refereed) Published
Abstract [en]

In molecular dynamics simulations utilizing enhanced-sampling techniques, reweighting is a central component for recovering the targeted ensemble averages of the unbiased system by calculating and applying a bias-correction function c(t). We present enhanced reweighting protocols for variationally enhanced sampling (VES) simulations by exploiting a recent reweighting method, originally introduced in the metadynamics framework [Giberti et al. J. Chem. Theory Comput., 2020, 16, 100-107], which was modified and extended to multiple-walker simulations: these may be implemented either as independent walkers (associated with one unique correction function per walker) or cooperative ones that all share one correction function, which is the hitherto only explored option. When each case is combined with the two possibilities of determining c(t) by time integration up to either t or over the entire simulation period , altogether four reweighting options result. Their relative merits were assessed by well-tempered VES simulations of two model problems: locating the free-energy difference between two metastable molecular conformations of the N-acetyl-l-alanine methylamide dipeptide, and the recovery of an a priori known distribution when one water molecule in the liquid phase is perturbed by a periodic free-energy function. The most rapid convergence occurred for large cooperative walkers, regardless of the upper integration limit, but integrating up to t proved advantageous for small walker ensembles. That novel reweighting method compared favorably to the standard VES reweighting, as well as to current state-of-the-art reweighting options introduced for metadynamics simulations that estimate c(t) by integration over the collective variables. For further gains in computational speed and accuracy, we also introduce analytical solutions for c(t), as well as offering further insight into its features by approximative analytical expressions in the high-temperature regime.

National Category
Theoretical Chemistry Other Physics Topics
Identifiers
urn:nbn:se:su:diva-221112 (URN)10.1039/d2cp04009c (DOI)001045147500001 ()37560777 (PubMedID)2-s2.0-85168627415 (Scopus ID)
Available from: 2023-09-19 Created: 2023-09-19 Last updated: 2023-09-19Bibliographically approved
Edén, M. (2023). Probing oxide-based glass structures by solid-state NMR: Opportunities and limitations. Journal of magnetic resonance open, 16-17, Article ID 100112.
Open this publication in new window or tab >>Probing oxide-based glass structures by solid-state NMR: Opportunities and limitations
2023 (English)In: Journal of magnetic resonance open, ISSN 2666-4410, Vol. 16-17, article id 100112Article in journal (Refereed) Published
Abstract [en]

This Primer critically reviews the possibilities and limitations of probing the short-range structure of an oxide-based glass by routine magic-angle spinning (MAS) or triple-quantum MAS (3QMAS) nuclear magnetic resonance (NMR) experiments. We briefly outline the structural features of oxide-based glasses and the basics of solid-state NMR. Besides suggesting guidelines for selecting favorable experimental conditions and important considerations for recording high-quality MAS NMR spectra amenable for subsequent analysis, we review options for extracting NMR observables and their distributions from spins-1/2 as well as half-integer spin quadrupolar nuclei. Considering that the isotropic chemical shift remains the primary probe of local structure by MAS NMR, we thoroughly review its dependence on the short-range oxide-based glass parameters from the viewpoint of a very simple and intuitive but qualitative model. The utility of deconvolutions of notably 29Si and 31P MAS NMR spectra are discussed critically. We also suggest alternative yet qualitative analysis options that are available whenever MAS NMR spectral deconvolutions are not warranted without additional information, which incidentally applies to a majority of modern multicomponent glasses.

Keywords
Glass structure, Cation field strength, Chemical shift, Parameter distributions, Half-integer spin quadrupolar nuclei
National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-225430 (URN)10.1016/j.jmro.2023.100112 (DOI)001133188700001 ()2-s2.0-85162927871 (Scopus ID)
Available from: 2024-01-17 Created: 2024-01-17 Last updated: 2024-01-17Bibliographically approved
Lv, Z.-P., Wang, C., Stevensson, B., Yu, Y., Wang, T. & Edén, M. (2022). Impact of the cation field strength on physical properties and structures of alkali and alkaline-earth borosilicate glasses. Ceramics International, 48(13), 18094-18107
Open this publication in new window or tab >>Impact of the cation field strength on physical properties and structures of alkali and alkaline-earth borosilicate glasses
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2022 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 48, no 13, p. 18094-18107Article in journal (Refereed) Published
Abstract [en]

The impact of the cation field strength (CFS) of the glass network-modifier cations on the structure and properties of borosilicate glasses (BS) were examined for a large ensemble of mixed-cation (R/2)M(2)O–(R/2)Na2O–B2O3–KSiO2 glasses with M+ ={Li+, Na+, K+, Rb+} and M2+ ={Mg2+, Ca2+, Sr2+, Ba2+} from four series of {K, R} combinations of K = n(SiO2)/n(B2O3) = {2.0, 4.0} and R =[n(M(2)O) ​+ ​n(Na2O)]/n(B2O3) = {0.75, 2.1}. Combined with results from La3+ bearing glasses enabled the probing of physical-property variations across a wide CFS range, encompassing the glass transition temperature (Tg), density, molar volume and compactness, as well as the hardness (H) and Young's modulus (E). We discuss the inferred composition–structure/CFS–property relationships. Each of Tg, H, and E revealed a non-linear dependence against the CFS and a strong Tg/H correlation, where each property is maximized for the largest alkaline-earth metal cations, i.e., Sr2+ and Ba2+, along with the high-CFS La3+ species. The 11B MAS NMR-derived fractional BO4 populations decreased linearly with the average Mz+/Na+ CFS within both K–0.75 glass branches, whereas the NBO-rich K–2.1 glasses manifested more complex trends. Comparisons with results from RM2O–B2O3–KSiO2 glasses suggested no significant “mixed alkali effect”.

Keywords
Borosilicate glass, Composition-structure-property relations, Cation field strength, Glass structure, 11B MAS NMR
National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-206190 (URN)10.1016/j.ceramint.2022.03.022 (DOI)000807125100004 ()2-s2.0-85128197553 (Scopus ID)
Available from: 2022-06-22 Created: 2022-06-22 Last updated: 2022-08-15Bibliographically approved
Karlsson, S., Mathew, R., Ali, S., Paemurru, M., Anton, J., Stevensson, B. & Edén, M. (2022). Mechanical, thermal, and structural investigations of chemically strengthened Na2O–CaO–Al2O3–SiO2 glasses. Frontiers in Materials, 9, Article ID 953759.
Open this publication in new window or tab >>Mechanical, thermal, and structural investigations of chemically strengthened Na2O–CaO–Al2O3–SiO2 glasses
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2022 (English)In: Frontiers in Materials, ISSN 2296-8016, Vol. 9, article id 953759Article in journal (Refereed) Published
Abstract [en]

For a series of conventional soda-lime-silicate glasses with increasing Al2O3 content, we investigated the thermal, mechanical, and structural properties before and after K+-for-Na+ ion-exchange strengthening by exposure to molten KNO3. The Al-for-Si replacement resulted in increased glass network polymerization and lowered compactness. The glass transition temperature (Tg), hardness (H) and reduced elastic modulus (Er), of the pristine glasses enhanced monotonically for increasing Al2O3 content. H and Er increased linearly up to a glass composition with roughly equal stoichiometric amounts of Na2O and Al2O3 where a nonlinear dependence on Al2O3 was observed, whereas H and Er of the chemically strengthened (CS) glasses revealed a strictly linear dependence. Tg, on the other hand, showed linear increase with Al-for-Si for pristine glasses while for the CS glasses a linear to nonlinear trend was observed. Solid-state 27Al nuclear magnetic resonance (NMR) revealed the sole presence of AlO4 groups in both the pristine and CS glasses. 23Na NMR and wet-chemical analysis manifested that all Al-bearing glasses had a lower and near-constant K+-for-Na+ ion exchange ratio than the soda-lime-silicate glass. Differential thermal analysis of CS glasses revealed a “blurred” glass transition temperature (Tg) and an exothermic step below Tg; the latter stems from the relaxation of residual compressive stresses. The nanoindentation-derived hardness at low loads and <5 mol% Al2O3 showed evidence of stress relaxation for prolonged ion exchange treatment. The crack resistance is maximized for molar ratios n(M(2)O)/n(Al2O3)≈1≈1 for the CS glasses, which is attributed to an increased elastic energy recovery that is linked to the glass compactness

Keywords
ion exchange, soda-lime-silicate glass, aluminosilicate glass, strengthening, nanoindentation, glass transition temperature, MAS NMR, network connectivity
National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-211527 (URN)10.3389/fmats.2022.953759 (DOI)000876509100001 ()2-s2.0-85140578713 (Scopus ID)
Available from: 2022-11-23 Created: 2022-11-23 Last updated: 2022-11-28Bibliographically approved
Mathew, R., Stevensson, B., Pujari-Palmer, M., Wood, C. S., Chivers, P. R. .., Spicer, C. D., . . . Edén, M. (2022). Nuclear Magnetic Resonance and Metadynamics Simulations Reveal the Atomistic Binding of ʟ-Serine and O-Phospho-ʟ-Serine at Disordered Calcium Phosphate Surfaces of Biocements. Chemistry of Materials, 34(19), 8815-8830
Open this publication in new window or tab >>Nuclear Magnetic Resonance and Metadynamics Simulations Reveal the Atomistic Binding of ʟ-Serine and O-Phospho-ʟ-Serine at Disordered Calcium Phosphate Surfaces of Biocements
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2022 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 34, no 19, p. 8815-8830Article in journal (Refereed) Published
Abstract [en]

Interactions between biomolecules and structurally disordered calcium phosphate (CaP) surfaces are crucial for the regulation of bone mineralization by noncollagenous proteins, the organization of complexes of casein and amorphous calcium phosphate (ACP) in milk, as well as for structure–function relationships of hybrid organic/inorganic interfaces in biomaterials. By a combination of advanced solid-state NMR experiments and metadynamics simulations, we examine the detailed binding of O-phospho-l-serine (Pser) and l-serine (Ser) with ACP in bone-adhesive CaP cements, whose capacity of gluing fractured bone together stems from the close integration of the organic molecules with ACP over a subnanometer scale. The proximity of each carboxy, aliphatic, and amino group of Pser/Ser to the Ca2+ and phosphate species of ACP observed from the metadynamics-derived models agreed well with results from heteronuclear solid-state NMR experiments that are sensitive to the 13C–31P and 15N–31P distances. The inorganic/organic contacts in Pser-doped cements are also contrasted with experimental and modeled data on the Pser binding at nanocrystalline HA particles grown from a Pser-bearing aqueous solution. The molecular adsorption is driven mainly by electrostatic interactions between the negatively charged carboxy/phosphate groups and Ca2+ cations of ACP, along with H bonds to either protonated or nonprotonated inorganic phosphate groups. The Pser and Ser molecules anchor at their phosphate/amino and carboxy/amino moieties, respectively, leading to an extended molecular conformation across the surface, as opposed to an “upright standing” molecule that would result from the binding of one sole functional group.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-210662 (URN)10.1021/acs.chemmater.2c02112 (DOI)000862981000001 ()36248225 (PubMedID)2-s2.0-85139264688 (Scopus ID)
Available from: 2022-11-23 Created: 2022-11-23 Last updated: 2023-01-02Bibliographically approved
Stevensson, B. & Edén, M. (2021). Exotic structural motifs in aluminosilicate glasses quantified by solid-state NMR and molecular dynamics simulations. Journal of Non-Crystalline Solids, 569, Article ID 120389.
Open this publication in new window or tab >>Exotic structural motifs in aluminosilicate glasses quantified by solid-state NMR and molecular dynamics simulations
2021 (English)In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 569, article id 120389Article in journal (Refereed) Published
Abstract [en]

Conventional structural models of aluminosilicate (AS) glasses assume that there are no direct bonds between four-coordinated Al (Al[4]) species and non-bridging oxygen (NBO) anions, along with the (near) absence of Al[4]–O–Al[4] linkages (the “Loewenstein Al avoidance rule”). Yet, accumulating evidence from advanced solid-state NMR experiments on AS glasses that incorporate (moderately) high field-strength cations, notably so those of rare-earth metals (RE3+), reveal significant Al[4]–NBO and Al[4]–O–Al[4] populations. Here we review such NMR experimentation that enable a direct probing of these “exotic” structural motifs. We also re-analyze and discuss previously presented experimental and modeling results of a large set of RE2O3–Al2O3–SiO2 glasses with RE={La, Y, Lu, Sc}, where the structure/composition-related parameters that dictate the degrees of Al[4]–NBO and Al[4]–O–Al[4] bonding in AS glasses are identified, leading to new quantitative composition–structure relationships. Moreover, for a given AS composition, criteria are presented for whenever Al[4]–O–Al[4] linkages must exit in its glass structure.

Keywords
Advanced NMR experimentation, Glass structure, Cation field-strength, Loewenstein Al avoidance, Al-NBO bonds, Composition-structure relationships
National Category
Materials Engineering
Identifiers
urn:nbn:se:su:diva-195983 (URN)10.1016/j.jnoncrysol.2020.120389 (DOI)000669571500009 ()
Available from: 2021-08-31 Created: 2021-08-31 Last updated: 2022-02-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9409-2601

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