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Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
HoNdFe14B crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ho is bonded in a 1-coordinate geometry to one Ho, two equivalent Nd, sixteen Fe, and one B atom. The Ho–Ho bond length is 3.59 Å. Both Ho–Nd bond lengths are 3.75 Å. There are a spread of Ho–Fe bond distances ranging from 3.01–3.35 Å. The Ho–B bond length is 2.86 Å. Nd is bonded in a 6-coordinate geometry to two equivalent Ho, sixteen Fe, and two equivalent B atoms. There are a spread of Nd–Fe bond distances ranging from 3.02–3.21 Å. Both Nd–B bond lengths are 3.26 Å. There are six inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted single-bond geometry to one Ho, one Nd, seven Fe, and one B atom. There are a spread of Fe–Fe bond distances ranging from 2.43–2.73 Å. The Fe–B bond length is 2.08 Å. In the second Fe site, Fe is bonded in a 2-coordinate geometry to one Ho, one Nd, and twelve Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.62–2.78 Å. In the third Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ho, one Nd, and nine Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.37–2.50 Å. In the fourth Fe site, Fe is bonded in a distorted q6 geometry to one Ho, one Nd, and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.45–2.53 Å. In the fifth Fe site, Fe is bonded in a distorted L-shaped geometry to two equivalent Nd, four Fe, and two equivalent B atoms. Both Fe–B bond lengths are 2.07 Å. In the sixth Fe site, Fe is bonded to two equivalent Ho, two equivalent Nd, and eight Fe atoms to form corner-sharing FeNd2Ho2Fe8 cuboctahedra. B is bonded in a 6-coordinate geometry to one Ho, two equivalent Nd, and six Fe atoms.
HoRuB4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Ho3+ is bonded in a 2-coordinate geometry to fourteen B+1.50- atoms. There are a spread of Ho–B bond distances ranging from 2.63–2.77 Å. Ru3+ is bonded in a 10-coordinate geometry to ten B+1.50- atoms. There are a spread of Ru–B bond distances ranging from 2.25–2.40 Å. There are four inequivalent B+1.50- sites. In the first B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Ho3+, two equivalent Ru3+, and three B+1.50- atoms. There are a spread of B–B bond distances ranging from 1.75–1.87 Å. In the second B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Ho3+, two equivalent Ru3+, and three B+1.50- atoms. The B–B bond length is 1.84 Å. In the third B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to four equivalent Ho3+, two equivalent Ru3+, and three B+1.50- atoms. There is one shorter (1.74 Å) and one longer (1.76 Å) B–B bond length. In the fourth B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to two equivalent Ho3+, four equivalent Ru3+, and three B+1.50- atoms. The B–B bond length is 1.72 Å.
HoSc(BO3)2 is Calcite-derived structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Ho3+ is bonded to six equivalent O2- atoms to form HoO6 octahedra that share corners with six equivalent ScO6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Ho–O bond lengths are 2.30 Å. Sc3+ is bonded to six equivalent O2- atoms to form ScO6 octahedra that share corners with six equivalent HoO6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Sc–O bond lengths are 2.14 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. O2- is bonded in a distorted trigonal planar geometry to one Ho3+, one Sc3+, and one B3+ atom.
Ho2Cu(B2O5)2 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.21–2.61 Å. Cu2+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share corners with six BO4 tetrahedra and edges with two equivalent BO4 tetrahedra. There are a spread of Cu–O bond distances ranging from 1.96–2.35 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share corners with two equivalent CuO6 octahedra and corners with three equivalent BO4 tetrahedra. The corner-sharing octahedra tilt angles range from 67–70°. There are a spread of B–O bond distances ranging from 1.43–1.56 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share a cornercorner with one CuO6 octahedra, corners with three equivalent BO4 tetrahedra, and an edgeedge with one CuO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of B–O bond distances ranging from 1.44–1.53 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+, one Cu2+, and one B3+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ho3+, one Cu2+, and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+, one Cu2+, and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ho3+ and one B3+ atom.
Compositionally complex oxides have garnered attention recently for their potential technological applications in harsh environments such as thermal barrier coatings and nuclear waste forms. Therefore, their response to extreme conditions, including high temperature and intense irradiation fields, must be thoroughly investigated. Here, the structural evolution of two pyrochlore oxides with comparable cation size ratio, r A /r B , (Yb 0.2 Er 0.2 Dy 0.2 Tb 0.2 Gd 0.2 ) 2 Ti 2 O 7 and Ho 2 Ti 2 O 7 , was evaluated after irradiation with 946 MeV Au ions up to a fluence of 8 × 10 12 ions/cm2 using synchrotron X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The overall radiation response is comparable for both titanate oxides and is dominated by a loss of crystallinity. When compared to a series of conventional titanate pyrochlore compositions, the amorphous track diameter of (Yb 0.2 Er 0.2 Dy 0.2 Tb 0.2 Gd 0.2 ) 2 Ti 2 O 7 is slightly larger than that of Ho2Ti2O7 and more in line with the diameter of the endmember with the maximum A-site cation size (Gd 2 Ti 2 O 7 ). Density functional theory calculations suggest that this behavior may be linked to local lattice distortions and the associated energetics of cation antisite formation. TEM and Raman analyses show that a disordered, crystalline shell surrounds the amorphous ion tracks in (Yb 0.2 Er 0.2 Dy 0.2 Tb 0.2 Gd 0.2 ) 2 Ti 2 O 7 , and the corresponding short-range structure resembles a weberite-type atomic arrangement.
High-speed computer-controlled switch-matrix system developed for communication satellites. Satellite system controlled by onboard computer and all message-routing functions between uplink and downlink beams handled by newly developed switch-matrix system. Message requires only 2-microsecond interconnect period, repeated every millisecond.
Mixed-valence dilanthanide complexes of the type (Cp iPr5 ) 2 Ln 2 I 3 (Cp iPr5 = pentaisopropylcyclopentadienyl; Ln = Gd, Tb, Dy) featuring a direct Ln–Ln σ-bonding interaction have been shown to exhibit well-isolated high-spin ground states and, in the case of the Tb and Dy variants, a strong axial magnetic anisotropy that gives rise to a large magnetic coercivity. Here, we report the synthesis and characterization of two new mixed-valence dilanthanide compounds in this series, (Cp iPr5 ) 2 Ln 2 I 3 (1-Ln; Ln = Ho, Er). Both compounds feature a Ln–Ln bonding interaction, the first such interaction in any molecular compounds of Ho or Er. Like the Tb and Dy congeners, both complexes exhibit high-spin ground states arising from strong spin–spin coupling between the lanthanide 4f electrons and a single σ-type lanthanide–lanthanide bonding electron. Beyond these similarities, however, the magnetic properties of the two compounds diverge. In particular, 1-Er does not exhibit observable magnetic blocking or slow magnetic relaxation, while 1-Ho exhibits magnetic blocking below 28 K, which is the highest temperature among Ho-based single-molecule magnets, and a spin reversal barrier of 556(4) cm –1 . Additionally, variable-field magnetization data collected for 1-Ho reveal a coercive field of greater than 32 T below 8 K, more than 6-fold higher than observed for the bulk magnets SmCo 5 and Nd 2 Fe 14 B, and the highest coercive field reported to date for any single-molecule magnet or molecule-based magnetic material. Multiconfigurational calculations, supported by far-infrared magnetospectroscopy data, reveal that the stark differences in magnetic properties of 1-Ho and 1-Er arise from differences in the local magnetic anisotropy of the lanthanide centers.
Ho4BO7Cl crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.22–2.35 Å. In the second Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to six O2- and one Cl1- atom. There are a spread of Ho–O bond distances ranging from 2.26–2.38 Å. The Ho–Cl bond length is 2.96 Å. In the third Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.25–2.76 Å. In the fourth Ho3+ site, Ho3+ is bonded in a 5-coordinate geometry to five O2- and one Cl1- atom. There are a spread of Ho–O bond distances ranging from 2.20–2.34 Å. The Ho–Cl bond length is 2.88 Å. B3+ is bonded in a trigonal planar geometry to three O2- atoms. All B–O bond lengths are 1.38 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of distorted corner and edge-sharing OHo4 tetrahedra. In the second O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Ho3+ and one B3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ho3+ and one B3+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to three Ho3+ and one B3+ atom. In the sixth O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the seventh O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. Cl1- is bonded in a 2-coordinate geometry to two Ho3+ atoms.
Numerous experimental investigations indicated that expansive clays such as montmorillonite can intercalate CO 2 preferentially into their interlayers and therefore potentially act as a material for CO 2 separation, capture, and storage. However, an understanding of the energy–structure relationship during the intercalation of CO 2 into clay interlayers remains elusive. Here, in this study, we use metadynamics molecular dynamics simulations to elucidate the energy landscape associated with CO 2 intercalation. Our free energy calculations indicate that CO 2 favorably partitions into nanoconfined water in clay interlayers from a gas phase, leading to an increase in the CO 2 /H 2 O ratio in clay interlayers as compared to that in bulk water. CO 2 molecules prefer to be located at the centers of charge-neutral hydrophobic siloxane rings, whereas interlayer spaces close to structural charges tend to avoid CO 2 intercalation. The structural charge distribution significantly affects the amount of CO 2 intercalated in the interlayers. These results provide a mechanistic understanding of CO 2 intercalation in clays for CO 2 separation, capture, and storage.
HoBO3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.25–2.48 Å. In the second Ho3+ site, Ho3+ is bonded to eight O2- atoms to form HoO8 hexagonal bipyramids that share corners with two equivalent HoO8 hexagonal bipyramids, corners with two equivalent BO4 tetrahedra, and edges with four equivalent BO4 tetrahedra. There are a spread of Ho–O bond distances ranging from 2.28–2.44 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share corners with two BO4 tetrahedra and edges with two equivalent HoO8 hexagonal bipyramids. There is two shorter (1.45 Å) and two longer (1.51 Å) B–O bond length. In the second B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share corners with two equivalent HoO8 hexagonal bipyramids and corners with two equivalent BO4 tetrahedra. There is two shorter (1.46 Å) and two longer (1.52 Å) B–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ho3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three Ho3+ and one B3+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Ho3+ and one B3+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ho3+ and two equivalent B3+ atoms.
Abstract Background Zymomonas mobilis has recently been shown to be capable of producing the valuable platform biochemical, 2,3-butanediol (2,3-BDO). Despite this capability, the production of high titers of 2,3-BDO is restricted by several physiological parameters. One such bottleneck involves the conversion of acetoin to 2,3-BDO, a step catalyzed by 2,3-butanediol dehydrogenase (Bdh). Several Bdh enzymes have been successfully expressed in Z. mobilis, although a highly active enzyme is yet to be identified for expression in this host. Here, we report the application of a phylogenetic approach to identify and characterize a superior Bdh, followed by validation of its structural attributes using a mutagenesis approach. Results Of the 11 distinct bdh genes that were expressed in Z. mobilis, crude extracts expressing Serratia marcescens Bdh ( Sm Bdh) were found to have the highest activity (8.89 µmol/min/mg), when compared to other Bdh enzymes (0.34–2.87 µmol/min/mg). The Sm Bdh crystal structure was determined through crystallization with cofactor (NAD + ) and substrate (acetoin) molecules bound in the active site. Active Sm Bdh was shown to be a tetramer with the active site populated by a Gln247 residue contributed by the diagonally opposite subunit. Sm Bdh showed a more extensive supporting hydrogen-bond network in comparison to the other well-studied Bdh enzymes, which enables improved substrate positioning and substrate specificity. This protein also contains a short α6 helix, which provides more efficient entry and exit of molecules from the active site, thereby contributing to enhanced substrate turnover. Extending the α6 helix to mimic the lower activity Enterobacter cloacae ( Ec Bdh) enzyme resulted in reduction of Sm Bdh function to nearly 3% of the total activity. In great contrast, reduction of the corresponding α6 helix of the Ec Bdh to mimic the Sm Bdh structure resulted in ~ 70% increase in its activity. Conclusions This study has demonstrated that Sm Bdh is superior to other Bdhs for expression in Z. mobilis for 2,3-BDO production. Sm Bdh possesses unique structural features that confer biochemical advantage to this protein. While coordinated active site formation is a unique structural characteristic of this tetrameric complex, the smaller α6 helix and extended hydrogen network contribute towards improved activity and substrate promiscuity of the enzyme.
Understanding thermochemical transformations of formic acid (FA) on metal oxide surfaces is important for many catalytical reactions. Here we study thermally induced reactions of FA on a single-crystalline and nanocrystalline anatase TiO 2 (101). We employ a combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory (DFT) to follow the FA surface intermediates and reaction products above room temperature. We find that the primary reaction products desorbing at about 300, 480, and 515 K are molecular water, carbon monoxide, and formaldehyde, respectively. Bidentate (BD) formate and bridging hydroxyl (HO b ) are identified as central intermediates in the FA transformations. Bridging oxygen vacancies (V O ) are also likely participants despite their low stability at the surface. In conclusion, the parallel studies on single crystals and faceted TiO 2 (101) nanoparticles reveal the spectroscopic commonalities of surface species and of the thermal conversion of molecular and deprotonated forms of FA.
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Ho2Fe14B is beta Uranium-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a 10-coordinate geometry to sixteen Fe atoms. There are a spread of Ho–Fe bond distances ranging from 2.98–3.19 Å. In the second Ho site, Ho is bonded in a 1-coordinate geometry to sixteen Fe and one B atom. There are a spread of Ho–Fe bond distances ranging from 3.03–3.35 Å. The Ho–B bond length is 2.86 Å. There are six inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted L-shaped geometry to two equivalent Ho, four Fe, and two equivalent B atoms. There are two shorter (2.49 Å) and two longer (2.73 Å) Fe–Fe bond lengths. Both Fe–B bond lengths are 2.06 Å. In the second Fe site, Fe is bonded to three Ho and nine Fe atoms to form distorted FeHo3Fe9 cuboctahedra that share corners with fourteen FeHo3Fe9 cuboctahedra, edges with three FeHo3Fe9 cuboctahedra, and faces with twelve FeHo2Fe10 cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.36–2.77 Å. In the third Fe site, Fe is bonded in a distorted single-bond geometry to two Ho, seven Fe, and one B atom. There are a spread of Fe–Fe bond distances ranging from 2.44–2.72 Å. The Fe–B bond length is 2.06 Å. In the fourth Fe site, Fe is bonded to four Ho and eight Fe atoms to form a mixture of face and corner-sharing FeHo4Fe8 cuboctahedra. All Fe–Fe bond lengths are 2.43 Å. In the fifth Fe site, Fe is bonded in a 2-coordinate geometry to two Ho and twelve Fe atoms. There are two shorter (2.61 Å) and two longer (2.63 Å) Fe–Fe bond lengths. In the sixth Fe site, Fe is bonded to two Ho and ten Fe atoms to form a mixture of distorted face, edge, and corner-sharing FeHo2Fe10 cuboctahedra. There are two shorter (2.54 Å) and one longer (2.55 Å) Fe–Fe bond lengths. B is bonded in a 6-coordinate geometry to one Ho and six Fe atoms.
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In low-temperature flash photolysis of NH 3 /O 2 /N 2 mixtures, the NH 2 consumption rate and the product distribution is controlled by the reactions NH 2 + HO 2 → products (R1), NH 2 + H (+M) → NH 3 (+M) (R2), and NH 2 + NH 2 (+M) → N 2 H 4 (+M) (R3). In the present work, published flash photolysis experiments by, among others, Cheskis and co-workers, are re-interpreted using recent direct measurements of NH 2 + H (+N 2 ) and NH 2 + NH 2 (+N 2 ) from Altinay and Macdonald. To facilitate analysis of the FP data, relative third-body collision efficiencies compared to N 2 for R2 and R3 were calculated for O 2 and NH 3 as well as for other selected molecules. We report results were in good agreement with the limited experimental data. Based on reported NH 2 decay rates in flash photolysis of NH 3 /O 2 /N 2 , a rate constant for NH 2 + HO 2 → NH 3 + O 2 (R1a) of $k_{1\text{a}}$ = 1.5(±0.5) × 10 14 cm 3 mol –1 s –1 at 295 K was derived. This value is higher than earlier determinations based on the FP results but in good agreement with recent theoretical work. Kinetic modeling of reported N 2 O yields indicates that NH 2 + HO 2 → H 2 NO + O (R1c) is competing with R1a, but perturbation experiments with addition of CH4 indicate that it is not a dominating channel. Measured HNO profiles indicate that this component is formed directly by NH 2 + HO 2 → HNO + H 2 O (R1b), but theoretical work indicates that R1b is only a minor channel. Based on this analysis, we estimate $k_{1\text{c}}$ = 2.5 × 10 13 cm 3 mol –1 s –1 and $k_{1\text{b}}$ = 2.5 × 10 12 cm 3 mol –1 s –1 at 295 K, with significant uncertainty margins.
Atomic spin centers in 2D materials are a highly anticipated building block for quantum technologies. Here, we demonstrate the creation of an effective spin-1/2 system via the atomically controlled generation of magnetic carbon radical ions (CRIs) in synthetic two-dimensional transition metal dichalcogenides. Hydrogenated carbon impurities located at chalcogen sites introduced by chemical doping are activated with atomic precision by hydrogen depassivation using a scanning probe tip. In its anionic state, the carbon impurity is computed to have a magnetic moment of 1 μ B resulting from an unpaired electron populating a spin-polarized in-gap orbital. We show that the CRI defect states couple to a small number of local vibrational modes. The vibronic coupling strength critically depends on the spin state and differs for monolayer and bilayer WS 2 . The carbon radical ion is a surface-bound atomic defect that can be selectively introduced, features a well-understood vibronic spectrum, and is charge state controlled.