State Of Na Research Articles

Anionic Redox Activities Boosted by Aluminum Doping in Layered Sodium-Ion Battery Electrode.

Sodium-ion batteries (SIBs) have attracted widespread attention for large-scale energy storage, but one major drawback, i.e., the limited capacity of cathode materials, impedes their practical applications. Oxygen redox reactions in layered oxide cathodes are proven to contribute additionally high specific capacity, while such cathodes often suffer from irreversible structural transitions, causing serious capacity fading and voltage decay upon cycling, and the formation process of the oxidized oxygen species remains elusive. Herein, a series of Al-doped P2-type Na0.6 Ni0.3 Mn0.7 O2 cathode materials for SIBs are reported and the corresponding charge compensation mechanisms are investigated qualitatively and quantitatively. The combined analyses reveal that Al doping boosts the reversible oxygen redox reactions through the reductive coupling reactions between orphaned O 2p states in NaOAl local configurations and Ni4+ ions, as directly evidenced by X-ray absorption fine structure results. Additionally, Al doping also induces an increased interlayer spacing and inhibits the unfavorable P2 to O2 phase transition upon desodiation/sodiation, which is common in P2-type Mn-based cathode materials, leading to the great improvement in capacity retention and rate capability. This work provides deeper insights into the development of structurally stable and high-capacity layered cathode materials for SIBs with anion-cation synergetic contributions.

Crystal Structures and Local Environments of NASICON-Type Na3FeV(PO4)3 and Na4FeV(PO4)3 Positive Electrode Materials for Na-Ion Batteries

In this work, we investigate the crystal chemistry of Fe/V-mixed NASICON Na 3 FeV(PO 4) 3 and Na 4 FeV(PO 4) 3 compositions structurally related to Na 3 V 2 (PO 4) 3 , a positive electrode for Naion batteries. To synthesize Na 4 FeV(PO 4) 3 , various synthesis routes (solid-state, sol-gel assisted, and electrochemical syntheses) were investigated. Direct syntheses resulted in forming a NASICON-type phase with the presence of NaFePO 4 and Na 3 PO 4 impurities. The successful preparation of pure Na 4 FeV(PO 4) 3 has been achieved by electrochemical sodiation of Na 3 FeV(PO 4) 3. Both synchrotron X-ray absorption and Mossbauer spectroscopies allowed probing the local V and Fe environments and their oxidation states in Na 3 FeV(PO 4) 3 and Na 4 FeV(PO 4) 3. Na 3 FeV(PO 4) 3 crystallizes in the space group C2/c (a = 15.1394(2) A; b = 8.72550(12) A; c = 21.6142(3) A; β = 90.1744(9)°, and Z = 12), and it is isostructural to an ordered α-form of Na 3 M 2 (PO 4) 3 (M = Fe, V). It presents a superstructure due to Na + ordering, as confirmed with differential scanning calorimetry and in situ temperature X-ray diffraction. The electrochemically-sodiated Na 4 FeV(PO 4) 3 powder crystallizes in the space group R-3c (a = 8.94656(8) A, c = 21.3054(3) A, and Z = 6) within which the two sodium sites, Na(1) and Na(2), are almost fully occupied. Na 4 FeV(PO 4) 3 allows the electrochemical extraction of 2.76 Na + per formula unit within the voltage range of 1.3-4.3 V vs. Na + /Na through the Fe III/II , V IV/III , and V V/IV redox couples. This identifies an interesting material for Na-ion batteries.

Final-state-resolved mutual neutralization of Na+ and D−

The present paper reports on a merged-beam experiment on mutual neutralization between ${\mathrm{Na}}^{+}$ and ${\mathrm{D}}^{\ensuremath{-}}$. For this experiment, we have used the DESIREE ion-beams storage-ring facility. The reaction products are detected using a position- and time-sensitive detector, which ideally allows for determination of the population of each individual quantum state in the final atomic systems. Here, the $4s, 3d$, and $4p$ final states in Na are observed and in all cases the D atom is in its ground state $1s ^{2}S$. The respective branching fractions of the states populated in Na are determined by fitting results from a Monte Carlo simulation of the experiment to the measured data. The center-of-mass collision energy is controlled using a set of biased drift tubes, and the branching fractions are measured for energies between 80 meV and 393 meV. The resulting branching fractions are found to agree qualitatively with the only available theoretical calculations for this particular system, which are based on a multichannel Landau-Zener approach using dynamic couplings determined with a linear combination of atomic orbitals model.

Investigation on the highly active SrTiO3 photocatalyst toward overall H2O splitting by doping Na ion

Photocatalytic properties of SrTiO3 doped with Na ion (Na+-SrTiO3) were investigated to develop the photocatalyst exhibiting high photocatalytic performances, not only the activity but also the durability for overall H2O splitting. The photocatalytic activity was remarkably improved by the introduction of a small amount of Na ion into SrTiO3 photocatalyst using rhodium and chromium mixed oxide (Rh0.7Cr1.3O3) as the co-catalyst. Moreover, the photocatalytic activity was influenced by the purity of the raw materials used for preparing Na+-SrTiO3 photocatalyst rather than the properties that originated with the preparation methods. The apparent quantum yield (AQY) of overall H2O splitting was 28% under the irradiation at 365 nm over the optimal Rh0.7Cr1.3O3/Na+-SrTiO3 photocatalyst. The photocatalytic performances of Rh2-yCryO3/Na+-SrTiO3 were confirmed to be further improved by separating the hydrogen evolution reaction (HER) site and the oxygen evolution reaction (OER) site over the surface by co-loading CoOx co-catalyst as OER sites. The states of Na+ doped SrTiO3 was investigated to make clear the key factors in the enhancement of the photocatalytic activity by the doping of aliovalent ions.

Topological Dirac Semimetal Phase in Bismuth Based Anode Materials for Sodium-Ion Batteries

Bismuth has recently attracted interest in connection with Na-ion battery anodes due to its high volumetric capacity. It reacts with Na to form Na 3 Bi which is a prototypical Dirac semimetal with a nontrivial electronic structure. Density-functional-theory based first-principles calculations are playing a key role in understanding the fascinating electronic structure of Na 3 Bi and other topological materials. In particular, the strongly-constrained-and-appropriately-normed (SCAN) meta-generalized-gradient-approximation (meta-GGA) has shown significant improvement over the widely used generalized-gradient-approximation (GGA) scheme in capturing energetic, structural, and electronic properties of many classes of materials. Here, we discuss the electronic structure of Na 3 Bi within the SCAN framework and show that the resulting Fermi velocities and s-band shift around the Γ point are in better agreement with experiments than the corresponding GGA predictions. SCAN yields a purely spin-orbit-coupling (SOC) driven Dirac semimetal state in Na 3 Bi in contrast with the earlier GGA results. Our analysis reveals the presence of a topological phase transition from the Dirac semimetal to a trivial band insulator phase in Na 3 Bi x Sb 1 − x alloys as the strength of the SOC varies with Sb content, and gives insight into the role of the SOC in modulating conduction properties of Na 3 Bi.

Degenerate ground state in the classical pyrochlore antiferromagnetNa3Mn(CO3)2Cl

In an ideal classical pyrochlore antiferromagnet without perturbations, an infinite degeneracy at a ground state leads to absence of a magnetic order and spin-glass transition. Here we present Na$_3$Mn(CO$_3$)$_2$Cl as a new candidate compound where classical spins are coupled antiferromagnetically on the pyrochlore lattice, and report its structural and magnetic properties.The temperature dependences of the magnetic susceptibility and heat capacity, and the magnetization curve are consistent with those of an $S$ = 5/2 pyrochlore lattice antiferromagnet with nearest-neighbor interactions of 2 K. Neither an apparent signature of a spin-glass transition nor a magnetic order is detected in magnetization and heat capacity measurements, or powder neutron diffraction experiments. On the other hand, an antiferromagnetic short-range order from the nearest neighbors is evidenced by the $Q$-dependence of the diffuse scattering which develops around 0.85 \AA$^{-1}$. A high degeneracy near the ground state in Na$_3$Mn(CO$_3$)$_2$Cl is supported by the magnetic entropy estimated as almost 4 J K$^{-2}$ mol$^{-1}$ at 0.5 K.

Theoretical study of 2s shell photoionization and subsequent Auger decay in atomic sodium

The 2s inner shell photoionization (PI) of Na and Auger decay of 1s22s2p63s state in Na+ were investigated using single-configuration and multiconfiguration (MC) approximation methods. The PI cross...

Islamic Military Alliance (IMA) – and Pakistan

The power politics and dominance are recurring features of Middle East which is in the continuous state of transformation ever since the Iranian revolution of 1979 and Soviet invasion of Afghanistan. The United States since the oil crises of 1970s has declared energy security. The unfortunate incident of 9/11 generated ferocious US response which was unleashed in the Middle East on the premise of regime change. This transition has proved to be uncertain and full of risks with catastrophic consequences and resultant rise of non- state (NSA) actors like ISIS and ISIL. This article unveils the basic contours and prime motives behind formation of IMA, its aims and objectives, analyses its efficacy in countering violent extremism with potential implications for Pakistan as a major stake holder and suggests a way forward for Pakistan to convert this into opportunity by mitigating challenges. This is academic narrative, views and comments are author’s own.

Vibrational spectra and analytical potential energy functions of some electronic states of Na2

The improved variational algebraic energy consistent method (VAECM) is suggested to study the vibrational spectra and analytical potential energy functions of six excited electronic states [Formula: see text], 21Δg, (5d)1Δg, (6d)1Δg, (7d)1Δg, and (8d)1Δg of Na2. The full vibrational energies, the vibrational spectroscopic constants, the force constants fn, and the expansion coefficients an of the potential are tabulated. The VAECM analytical potential energy function with adjustable parameter λ for each electronic state is determined. The full vibrational energies of each of these electronic states correctly converge to its dissociation energy and have no artificial barrier in all the calculation ranges. The VAECM analytical potentials excellently agree with the Rydberg–Klein–Rees potentials.

Accurate theoretical study on the ground and first-excited states of Na2: potential energy curves, spectroscopic parameters, and vibrational energy levels

Potential energy curves (PECs) for the ground and first-excited electronic states of Na2 are obtained by fitting the ab initio energies calculated at the MRCI(Q)/aug-cc-pVXZ (X = T, Q, 5) level of theory, which are subsequently extrapolated to the complete basis set limit. The relativistic effect and core–valence correlation are also considered. The PECs are accurate at both short and long internuclear distances with the root-mean-squared deviations being 0.72 cm−1 for Na2 [Formula: see text] and 0.36 cm−1 for Na2 [Formula: see text]. Utilizing the obtained PECs, we calculate the spectroscopic parameters, vibrational energy levels, classical turning points, inertial rotation, and centrifugal distortion constants, which are in good agreement with other theoretical and experimental work.

Folding dynamics and conformational heterogeneity of human telomeric G-quadruplex structures in Na+ solutions by single molecule FRET microscopy.

G-quadruplex structures can occur throughout the genome, including at telomeres. They are involved in cellular regulation and are potential drug targets. Human telomeric G-quadruplex structures can fold into a number of different conformations and show large conformational diversity. To elucidate the different G-quadruplex conformations and their dynamics, we investigated telomeric G-quadruplex folding using single molecule FRET microscopy in conditions where it was previously believed to yield low structural heterogeneity. We observed four FRET states in Na+ buffers: an unfolded state and three G-quadruplex related states that can interconvert between each other. Several of these states were almost equally populated at low to medium salt concentrations. These observations appear surprising as previous studies reported primarily one G-quadruplex conformation in Na+ buffers. Our results permit, through the analysis of the dynamics of the different observed states, the identification of a more stable G-quadruplex conformation and two transient G-quadruplex states. Importantly these results offer a unique view into G-quadruplex topological heterogeneity and conformational dynamics.

All-atom molecular dynamics simulations of an artificial sodium channel in a lipid bilayer: the effect of water solvation/desolvation of the sodium ion

All-atom molecular dynamics is used to investigate the transport of Na+ across a 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayer facilitated by a diazacrown hydraphile. Specifically, the free energy of Na+ passing through the bilayer is calculated using the adaptive biasing force method to study the free energy associated with the increase in Na+ transport in the presence of the hydraphile molecule. The results show that water interaction greatly influences Na+ transport through the lipid bilayer as water is pulled through the bilayer with Na+ forming a water channel. The hydraphile causes a reduction in the free energy barrier for the transport of Na+ through the head group part of the lipid bilayer since it complexes the Na+ reducing the necessity for water to be complexed and, therefore, dragged through with Na+, an energetically unfavorable process. The free energy associated with Na+ being desolvated within the bilayer is significantly decreased in the presence of the hydraphile molecule; the hydraphile increases the number of solvation states of Na+ that can be adopted, and this increase in the number of available configurations provides an entropic explanation for the success of the hydraphile.

Medium effect on dielectric relaxation behaviors of 4A zeolite bulk dispersion system

Abstract Dielectric spectra of 4A zeolite particles bulked in deionized water (4A/W) or cyclohexane (4A/C) were measured respectively under different temperatures, and two dielectric relaxations were found in both of 4A/W and 4A/C. Because of existence of water molecules in pores, both low and high frequency relaxation times (τLFR and τHFR) of 4A/W decreased more sharply than 4A/C with increasing temperature. According to the temperature dependence of τLFR and τHFR, the activation energies of Na+ interacting with framework under hydrated and dehydrated environments were calculated respectively, and the original properties of Na+ in dehydrated zeolite were obtained by analyzing the dielectric properties of 4A/C. Furthermore, a transient state of Na+ motion with temperature was found in 4A/C system.

Sensitivity to Aldosterone

See related article, p 1212–1218 In this issue, Tu et al1 show clear differences in sensitivity of blood pressure (BP) to aldosterone between blacks and those of predominantly white ancestry, in both children and adults. It has long been known that blacks are more salt sensitive than whites: this contribution thus complements the previous findings and has ramifications for the role of aldosterone across the board. The article reports the unusual combination of a long-term (>20 years) observational study on children aged 5 to 17 years starting in 1986 and an acute intervention study comparing the effects of fludrocortisone administration for 2 weeks on BP, weight, and hormonal parameters in black and white adults. The long-term study enrolled 580 children (266 blacks, 314 whites). Age, height, weight, systolic and diastolic BP (DBP), concentrations of plasma electrolytes (Na+ K+), plasma aldosterone (PAC), and renin activity (PRA) were measured, plus urinary excretion of Na+, K+, and creatinine. At baseline, black children were on average 18 months older, with a higher body mass index and slightly but significantly higher BP (103/43 versus 100/41 mm Hg). They also showed significantly lower PAC (9 versus 14 ng/dL) and PRA levels (2.8 versus 3.3 ng/mL per hour), with indistinguishable plasma [K+] and overnight urinary excretion levels of K+ and Na+. In the subsequently re-enrolled adult subcohort, the blacks were 17 months younger, with higher body mass index (31 versus 28) but identical systolic and DBP (116/74 mm Hg). They had lower levels of PRA (1.0 versus 1.5 ng/mL per hour) and PAC (5 versus 9 ng/dL), with levels of plasma K+ and BP indistinguishable from those in whites. Urinary Na+ excretion was similar (78 versus 81 nmol/mg creatinine), but K+ excretion …

The post-collision interaction effect in autoionizing spectra of alkali atoms excited by electron impact

Ejected-electron energy spectra resulting from decay of the (4p55s2)2P3/2, 1/2 autoionizing states in rubidium atoms have been studied at electron impact energies up to 5 eV above the excitation thresholds. The energy shift of corresponding lines due to the post-collision interaction (PCI) involving the outgoing electrons and the residual ion have been observed for the first time. For both states the energy dependence of the shift possesses a smooth asymptotic behaviour which is satisfactorily described by the classical model of the PCI effect. Similar behaviour of the line shift was reported earlier also for the (5p56s2)2P3/2 autoionizing state in heavier Cs atoms. Both results contrast with the clear oscillatory-like character of the line shift for the (np5[n + 1]s2)2P3/2, 1/2 autoionizing states in the lighter Na (n = 2) and K (n = 3) atoms. The comparative analysis of the data on the PCI effect and excitation cross-sections of the (np5[n + 1]s2)2P3/2, 1/2 autoionizing states in Na (n = 2), K (n = 3), Rb (n = 4) and Cs (n = 5) atoms has shown that the high polarizability of the resonantly excited target and partial structure of resonances are the main factors which determine the dynamics of the PCI shift of lines in ejected-electron spectra of alkali atoms.

Resonance excitation of the (4p55s2)2P3/2,1/2 autoionizing states in Rb atoms by electron impact

The near-threshold excitation dynamics of the 4p55s2 2P3/2,1/2 autoionizing states in rubidium atoms was studied experimentally by measuring the ejected-electron excitation functions and theoretically by applying a fully relativistic Dirac B-spline R-matrix (close-coupling) model. As in the previously studied np5(n+1)s2 2P3/2,1/2 states in Na (n=2), K (n=3), and Cs (n=5) atoms, strong negative-ion resonances dominate the electron-impact excitation of the lowest autoionizing states in Rb.

Abstract 625: Role Of Proximal Na+ Reabsorption In The Fructose-induced Hypertension

Methods/Results: Wistar rats were fed for 2 or 8 weeks with control diet (CTRL) or isocaloric 60% fructose diet (HF). Systolic blood pressure (SBP) was measured weekly by tail cuff plethysmography. There was no difference in the SBP (mmHg) after 2 weeks of HF intake (110 ± 1.7 CTRL x 121 ± 5.8 HF); however, there was an increase in SBP after 8 weeks (111.9 ± 1.3 CTRL x 143.3 ± 1.5 HF, P < 0.0001). Urine of 24h collected in metabolic cages showed a reduction in urine flow (mL/min) (2 weeks - 0.018 ± 0.002 CTRL x 0.009 ± 0.001 HF, P = 0.0007 and 8 weeks - 0.017 ± 0.002 CTRL x 0.007 ± 0.0004 HF, P = 0.001). Glomerular filtration rate (GFR) was not altered after 2 weeks (1.31 ± 0.3 CTRL x 1.22 ± 0.5 HF), but was decreased after 8 weeks (1.82 ± 0.4 CTRL x 0.37 ± 0.1 HF, P = 0.001). Na+ fractional excretion (Na-FE), in % of creatinine clearance, was decreased after 2 weeks (0.37 ± 0.05 CRTL x 0.13 ±0.03 HF), but was increased after 8 weeks (0.18 ± 0.06 CTRL x 0.54 ± 0.14 HF, P = 0.038). After 2 or 8 weeks, rats were subjected to in situ microperfusion experiments and had their proximal tubules (TP) perfused with an alkaline solution to investigate Na+ reabsorption by means of bicarbonate flux (JHCO3-, in nmol/cm2 x s). JHCO3- was increased after 2 weeks (1.78 ± 0.09 CTRL x 2.7 ± 0.14 HF), but was reduced after 8 weeks (2.00 ± 0.09 CRTL x 1.19 ± 0.04 HF). The perfusion of PT with S3226, a specific NHE3 inhibitor, showed that fructose acts stimulating NHE3 activity after 2 weeks (0.82 ± 0.09 CRTL + S3226 x 1.83 ± 0.14 HF + S3226, P < 0.0001) and inhibiting NHE3 activity after 8 weeks (0.85 ± 0.09 CRTL x 0.22 ± 0.04 HF, P < 0.0001). Conclusions: Reduced Na+-FE and urine flow, associated with increased NHE3 activity after 2 weeks of HF suggest that, initially, fructose leads to a state of Na+ overload, which may contribute to the development of hypertension observed after 8 weeks of HF intake. Kidney damage was increased after 8 weeks, since GFR was decreased, explaining the persistence of reduced urine flow, despite reduced NHE3 activity. These data, together with the increase in Na-FE and installation of hypertension, suggest that the mechanism of pressure-natriuresis was activated after 8 weeks, in order to compensate for volume expansion. Our data suggest a role of increased Na+ reabsorption in the development of fructose-induced hypertension.

(2,2′-Bipyridyl)-3-3′-diol in Nafion: Stabilization of Unusual Ground and Excited States

(2,2'-Bipyridyl)-3-3'-diol (BP(OH)(2)) undergoes excited state intramolecular double proton transfer (ESIDPT). The photophysics of this molecule has been investigated, in the highly acidic water channels inside nafion membrane. The dianionic enolate form of the dye, which is formed only in alkaline conditions in neat aqueous solutions, is found to be present in its excited state in native nafion membrane at low water content. This surprising phenomenon has been explained in the light of loss of protons from the fluorophore to the medium, due to increased electrostatic interactions with the pendant sulfonate groups of nafion, at the lower water content. This observation fortifies the model of microscopic interactions that we have proposed in recent past. Further, the ground state of the diketo form, observed only in neat aqueous solutions so far, is found to be present in Na(+)-exchanged membranes at lower levels of hydration. The steady-state spectral features of the dye is different in (CH(3))(4)N(+)-exchanged membranes than that of Na(+)-exchanged membranes, unlike in our earlier studies with coumarin 102 and 2-(2'-pyridyl)benzimidazole, here we observed formation of an unusual ground state in Na(+)-exchanged membranes, while no such feature was observed in (CH(3))(4)N(+)-exchanged membranes.

Conical intersections in 2 2E ′ states of Na 3 cluster

We perform ab initio calculation using MOLPRO on the 2 2E ′ and 1 2 A 1 ′ states of Na 3 cluster and explore for locating the point of conical intersections (CIs) in the configuration space (CS). The functional form of Non-Adiabatic Coupling Term (NACT) between the 2 2E ′ states indicates the presence of singularity at four points in the CS. While performing Adiabatic-to-Diabatic Transformation (ADT) [Chem. Phys. Lett. 35 (1975) 112] by employing three state NACTs, two diagonal elements of ADT matrix display four sign changes as a signature of four CIs. Moreover, the locations of those CIs are confirmed by Longuet-Higgins’ theorem.

The post-collision energy shift of the (np5(n + 1)s2)2P3/2 lines in autoionizing spectra of sodium (n = 2) and caesium (n = 5) atoms excited by electron impact

The energy shift of lines arising from the decay of the (np5(n + 1)s2)2P3/2 autoionizing states in Na (n = 2) and Cs (n = 5) atoms has been studied for the first time in ejected-electron spectra measured over the excess energy range −0.1 to 5.4 eV. In Na spectra, the energy dependence of the shift possesses a clear oscillatory-like character. In particular, the shift becomes of negative or positive sign depending on the presence or absence of a negative-ion resonance structure in the excitation function of the (2p53s2)2P3/2 state. Earlier, we reported a similar behaviour of the line shift for the (3p54s2)2P3/2 autoionizing state in K atoms. Though in Cs atoms the strong negative-ion resonance is also present close to the excitation threshold of the (5p56s2)2P3/2 state, in contrast to Na and K data, the energy dependence of the line shift possesses a smooth asymptotic behaviour described well by the classical model of the post-collision effect. The comparative analysis of the spectroscopic classification of the resonance structure in the excitation of the (np5(n + 1)s2)2P3/2 autoionizing states in Na, K and Cs atoms has shown that the observed effect most probably reflects the complication of the compound character of resonances. In whole, the obtained data show that under the condition of the high polarizability of a resonantly excited target the relation between polarization attraction, centrifugal and Coulomb repulsion becomes a crucial factor which determines the final energy distribution of outgoing electrons.