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This may be useful for the purposes of CASTEP calculations. I think.
Chemical Physics Letters
Volume 484, Issues 4-6, 7 January 2010, Pages 374-379
doi:10.1016/j.cplett.2009.11.041Bhakti S. Kulkarnia, Sailaja Krishnamurtyb and Sourav Pala,
Abstract
Periodic systems are best described by the pseudo-potential methods. However, the accuracy of its description depends on the cut-off of plane wave basis. This is much more critical in the case of weak interactions, where a clear understanding on the influence of plane wave cut-off on the structural and electronic properties is not readily available in the literature. In the present work, we have taken a metal substituted beta zeolite–H2O complex for understanding this objective. Our studies show that while a lower cut-off of 500 eV is sufficient for the convergence of the structural parameters, description of energy-dependent properties necessitates a high cut-off value.
Chemical Physics Letters
Volume 485, Issues 1-3, 18 January 2010, Pages 217-220
doi:10.1016/j.cplett.2009.11.066
Stephan Appelta, , Stefan Glögglerb, Friedrich W. Häsinga, Ulrich Sielinga, Ali Gordji Nejada and Bernhard Blümichb
Abstract
NMR spectroscopy for chemical analysis at high field employs precision measurements of resonance frequencies governed by chemical shift and nuclear spin interactions. At low field and in the absence of hetero-nuclear J-couplings the natural line width limits the chemical shift measurements. We have performed chemical-shift resolved proton NMR spectra in the milli-Tesla regime, and found that in the presence of hetero-nuclear J-coupling, proton chemical-shift differences smaller than the line width can be measured down to nuclear Larmor frequencies of 41 kHz. The measurement of J-couplings and chemical shifts with simple NMR devices operating in the milli-Tesla regime may develop as an attractive tool for chemical analysis.
Chemical Physics Letters
Volume 485, Issues 4-6, 26 January 2010, Pages 275-280
doi:10.1016/j.cplett.2009.12.054Andreas Brinkmanna, b, , Suresh Kumar Vasaa, Hans Janssena and Arno P.M. Kentgensa, ,
Abstract
We present our recent progress in the development of micro-magic-angle-spinning solenoid-based probeheads for the application in high-resolution 1H solid-state NMR of nanoliter sample volumes. The use of fused-silica capillaries as sample holders results in spectra without any 1H background signal. It is possible to obtain 1H spectra of 40–80 nl samples in a few scans. We obtained high-resolution 1H spectra employing different homonuclear decoupling sequences on powdered samples of l-alanine, the tripeptide AGG, and a single crystal of l-tyrosine·HCl. In addition, we recorded high-resolution two-dimensional proton-detected 1H–13C heteronuclear correlation spectra of [U-13C3, 15N]-l-alanine and AGG with natural abundant isotope distribution.
Chemical Physics Letters
Volume 485, Issues 4-6, 26 January 2010, Pages 335-342
doi:10.1016/j.cplett.2009.12.044
Ingo Scholza, Beat H. Meiera and Matthias Ernst, a,
Abstract
We describe a resonant second-order dipolar recoupling condition for magic-angle spinning (MAS) solid-state NMR where the active spins are irradiated by continuous-wave irradiation and the passive spins by a phase-alternating sequence. The phase-modulation frequency is matched to an integer multiple of the MAS frequency to produce a second-order homonuclear dipolar coupling Hamiltonian that promotes broadband homonuclear zero-quantum polarization transfer on the spin-locked active spins. The recoupling sequence is based on second-order cross terms between two heteronuclear dipolar couplings. Similarities and differences to the proton-assisted recoupling sequence are discussed.
Everyone loves 3H NMR!
Chemical Physics Letters
Volume 486, Issues 1-3, 5 February 2010, Pages 21-26
doi:10.1016/j.cplett.2009.12.087E. Elliott Burnella, Cornelis A. de Langeb, , Donatella Capitanic, Giancarlo Angelinic and Ornella Ursinic
Abstract
The NMR spectra of the tritiated isotopologues of methane dissolved in several nematic liquid-crystalline solvents are measured. The spectral parameters obtained agree extremely well with those predicted from earlier NMR studies of the deuterated isotopologues, providing excellent confirmation of the theory for vibration–reorientation interaction developed earlier.
Chemical Physics Letters
Volume 487, Issues 4-6, 5 March 2010, Pages 232-236
doi:10.1016/j.cplett.2010.01.040
Takahiro Iijimaa, Toshihiro Yamaseb, Masataka Tanshoc, Tadashi Shimizuc and Katsuyuki Nishimuraa, ,
Abstract
We report solid-state 95Mo NMR of MoV, MoV,VI and MoVI species in mixed-valence polyoxomolybdates (V, VI) with localized or delocalized d1 electrons. Parameters about chemical shift and quadrupole interactions of 95Mo in diamagnetic crystals of with localized electrons and
with delocalized ones were obtained by simulation of magic-angle-spinning (MAS) 95Mo NMR spectra. The isotropic and anisotropic chemical shifts of sites of MoV in 1 and MoV, VI in 2, respectively, exhibited absolute values quite larger than those of other MoVI sites, which is examined by quantum chemical calculations.
Chemical Physics Letters
Volume 487, Issues 4-6, 5 March 2010, Pages 285-290
doi:10.1016/j.cplett.2010.01.048
Arne Bressela, Jörg Freya, Urszula Filekb, Bogdan Sulikowskib, Dieter Freudec and Michael Hungera
Abstract
Dehydrated aluminumdodecatungstophosphate (AlPW12O40) was investigated by 27Al MAS NMR spectroscopy in magnetic fields of 9.4 and 17.6 T. Two kinds of octahedrally coordinated (δ27Al = 1–2 ppm, CQ = 2.4–2.5 MHz, and δ27Al = 4–6 ppm, CQ = 6.0–6.5 MHz), two kinds of penta-coordinated (δ27Al = 24–30 ppm, CQ = 7.0–7.3 MHz, and δ27Al = 44 ppm, CQ = 7.5–8.7 MHz), and a small amount of tetrahedrally coordinated aluminum cations (δ27Al = 65 ppm, CQ = 8.2–8.5 MHz) were found. Comparison with 1H MAS NMR spectroscopic studies indicates that the dehydroxylation of aluminum OH groups (δ1H = 4.2 ppm and 5.6 ppm) at temperatures of 473 and 573 K is accompanied by a partially irreversible change of the oxygen coordination of aluminum cations.
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Volume 488, Issues 1-3, 12 March 2010, Pages 10-16
doi:10.1016/j.cplett.2010.01.072Markus Weingartha, Geoffrey Bodenhausena, b and Piotr Tekelya
Abstract
We introduce a new dipolar recoupling scheme, dubbed PARIS-xy (phase-alternated recoupling irradiation scheme using orthogonal radio-frequency phases), to promote efficient broadband magnetization exchange between 13C nuclei using moderate radio-frequency amplitudes at very high magnetic field strengths and spinning speeds. Experimental observations for a wide range of spinning frequencies 30 
νrot 60 kHz and magnetic field strengths (B0 = 9.4, 17.6 and 21.2 T) are backed up by numerical simulations.
A solid-state NMR scheme dubbed PARIS-xy affords efficient low-power recoupling of dipolar interactions between nuclei such as carbon-13 over a wide range of isotropic chemical shifts. The scheme is suitable for very high magnetic fields up to 21.2 T (900 MHz) and spinning speeds up to 60 kHz.
***Chemical Physics Letters
Volume 488, Issues 4-6, 22 March 2010, Pages 168-172
doi:10.1016/j.cplett.2010.02.015
Péter Terleczkya and László Nyulászi
Abstract
The effect of the possible cell defects in the methane-hydrate crystal on the chemical shift of the carbon core has been investigated by DFT calculations. The clathrate structure was modeled as a water monolayer, in mono and bicavital clusters. The results show that the radius of the clathrate cell correlates with the chemical shielding of the carbon core. The calculated chemical shifts for the most stable clusters are in good agreement with the observed NMR signals supporting the previous spectral assignment. The occupancy of a neighbouring cell in a bicavital cluster has a small effect on the calculated NMR shift.
Chemical Physics Letters
Volume 489, Issues 1-3, 1 April 2010, Pages 35-38
doi:10.1016/j.cplett.2010.02.051Ibon Alkorta and José Elgueroa
Abstract
The seven stationary points of the methane hypersurface were first explored concerning geometries and energies to check previous data. On these geometries, absolute 1H and 13C NMR shieldings as well as 1J(CH) and 2J(HH) coupling constants were calculated. The results show important variations in the NMR parameters depending on the stationary point considered. Relationships have been found between the 1H and 13C shieldings and between these NMR parameters and the relative energy of the different species.
Chemical Physics Letters
Volume 489, Issues 1-3, 1 April 2010, Pages 107-112
doi:10.1016/j.cplett.2010.02.026
Patrick Giraudeaua, 1, Norbert Müllerb, Alexej Jerschowc and Lucio Frydmana
Abstract
Noise measurements of nuclear spin systems using a tuned circuit can reveal the signatures of two different phenomena: Thermal circuit noise absorbed by the spin system, and nuclear spin-noise leading to tiny fluctuating magnetization components. Polarization enhancement can increase the observed noise amplitudes due to an enlarged coupling with the reception circuit. In this work we explore the detection of noise in 1H NMR of liquid water samples whose spin alignment is enhanced via ex situ dynamic nuclear polarization. A number of ancillary phenomena related to this kind of experiments are also documented.
Chemical Physics Letters
Volume 489, Issues 4-6, 9 April 2010, Pages 248-253
doi:10.1016/j.cplett.2010.02.078
S. Begam Elavarasia and Kavita Doraib
Abstract
The 19F chemical shift anisotropy (CSA) tensor is an indispensable structure estimation tool in the NMR investigations of flourinated biomolecules. This work focuses on the characterization of the 19F CSA tensor in small molecules, through the combined use of quantum chemical methods and liquid-state NMR cross-correlated spin relaxation experiments. The effect of different basis sets and quantum computational methods on the magnitude and orientation of the 19F CSA tensor are discussed. The results from ab initio methods and the liquid-state relaxation experiments match well and are comparable to values of the CSA tensor obtained from previous solid-state studies and from theoretical investigations of similar molecules.
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