Molecular Conductance Research Articles

Stereoelectronic Switches of Single-Molecule Junctions through Conformation-Modulated Intramolecular Coupling Approaches.

Stereoelectronic effects in single-molecule junctions have been widely utilized to achieve a molecular switch, but high-efficiency and reproducible switching remain challenging. Here, we demonstrate that there are three stable intramolecular conformations in the 9,10-diphenyl-9,10-methanoanthracen-11-one (DPMAO) systems due to steric effect. Interestingly, different electronic coupling approaches including weak coupling (through-space), decoupling, and strong coupling (through-bond) between two terminal benzene rings are accomplished in the three stable conformations, respectively. Theoretical calculations show that the molecular conductance of three stable conformations differs by more than 1 order of magnitude. Furthermore, the populations of the three stable conformations are highly dependent on the solvent effect and the external electric field. Therefore, an excellent molecular switch can be achieved using the DPMAO molecule junctions and external stimuli. Our findings reveal that modulating intramolecular electronic coupling approaches may be a useful manner to enable molecular switches with high switching ratios. This opens up a new route for building high-efficiency molecular switches in single-molecular junctions.

Effect of fluorine substitution on the electronic states and conductance of CuPc on Cu(100)

The electronic states and conductance of CuPc, F8CuPc, and F16CuPc on Cu(100) were studied by using scanning tunneling microscopy (STM) and the density functional theory (DFT) calculations. For all molecules, the lowest unoccupied molecular orbital (LUMO) was observed around the Fermi level (EF), regardless of the difference in the original LUMO levels of the free molecules. This indicates that the strong interaction causes the pinning of EF at LUMO levels. Meanwhile, the differential conductance at EF is drastically affected by the substitution: it increases and decreases for CuPc and F16CuPc, respectively, suggesting that the Fano effect plays a major role in the conductance. This finding provides a new strategy for the control of molecular conductance by chemical substitution.

A predictive approach for the compositional and temperature representation of thermal conductivity in multicomponent molten salt systems for advanced energy applications

This study presents a theoretical model, based on kinetic theory, for accurately predicting thermal conductivity in molten salt mixtures, a vital factor in designing advanced energy systems such as concentrating solar power, thermal energy storage, and advanced nuclear reactors. Applicable to non-complex, non-reciprocal systems, the model represents thermal conductivity with respect to composition and temperature. We evaluated the model using molecular dynamics simulations on binary systems from fluoride, chloride, bromide, iodide salt families. The model predictions were also compared against existing experimental datasets for those families as well as binary nitrates and carbonates. The model demonstrated an improvement in predictive accuracy over the ideal linear estimation and showed reasonable agreement with the reliable experimental data. Deviations from ideal conductivity, analyzed using the Redlich-Kister method, pointed to the molecular weight and thermal conductivity of individual compounds as primary influencing factors. When applied to predict the thermal conductivity of higher order eutectic salt mixtures relevant to energy applications, the model showed predictive accuracy comparable to empirical methods. The model was further applied to generate compositional mapping to quantify deviations from ideality over the compositional space. This advance enhances new molten salt mixtures evaluation efficiency and extends the model to complex mixtures.

Quantum bath augmented stochastic nonequilibrium atomistic simulations for molecular heat conduction.

Classical molecular dynamics (MD) has been shown to be effective in simulating heat conduction in certain molecular junctions since it inherently takes into account some essential methodological components which are lacking in the quantum Landauer-type transport model, such as many-body full force-field interactions, anharmonicity effects and nonlinear responses for large temperature biases. However, the classical MD reaches its limit in the environments where the quantum effects are significant (e.g. with low-temperatures substrates, presence of extremely high frequency molecular modes). Here, we present an atomistic simulation methodology for molecular heat conduction that incorporates the quantum Bose-Einstein statistics into an "effective temperature" in the form of a modified Langevin equation. We show that the results from such a quasi-classical effective temperature MD method deviates drastically when the baths temperature approaches zero from classical MD simulations and the results converge to the classical ones when the bath approaches the high-temperature limit, which makes the method suitable for full temperature range. In addition, we show that our quasi-classical thermal transport method can be used to model the conducting substrate layout and molecular composition (e.g. anharmonicities, high-frequency modes). Anharmonic models are explicitly simulated via the Morse potential and compared to pure harmonic interactions to show the effects of anharmonicities under quantum colored bath setups. Finally, the chain length dependence of heat conduction is examined for one-dimensional polymer chains placed in between quantum augmented baths.

Laboratory equipment for practice learning in the framework of educational course “Molecular Physics and Thermodynamics”

This article presents laboratory equipment for practice learning of physics specialties students in the framework of educational course “Molecular Physics and Thermodynamics”. The presented laboratory equipment allows measuring the temperature dependence of the thermal conductivity coefficient of molecular liquids under atmospheric pressure and saturated vapors pressure in the temperature range from 150K to 400K. A general scheme of the developed experimental setup for measuring the thermal conductivity of liquids by the steady-state method under isobaric condition has been described. The created laboratory setup uses general design solutions of the coaxial cylinder method, preserving its features and measurement precision in general. The measurements are carried out on coaxial-geometry cell under atmospheric pressure. A modified heat potentiometer method with one thermometer was used, which allowed us to minimize the error in the estimation of the thermal conductivity coefficient due to the uncontrollable heat flows and different calibration of thermometers. The total systematic error in the measurement of the molecular liquids thermal conductivity does not exceed 3%. The procedures for direct measurement and calculation of the thermal conductivity coefficient of molecular liquids using the developed laboratory equipment are described.

High performance mechano-optoelectronic molecular switch

Highly-efficient molecular photoswitching occurs ex-situ but not to-date inside electronic devices due to quenching of excited states by background interactions. Here we achieve fully reversible in-situ mechano-optoelectronic switching in self-assembled monolayers (SAMs) of tetraphenylethylene molecules by bending their supporting electrodes to maximize aggregation-induced emission (AIE). We obtain stable, reversible switching across >1600 on/off cycles with large on/off ratio of (3.8 ± 0.1) × 103 and 140 ± 10 ms switching time which is 10-100× faster than other approaches. Multimodal characterization shows mechanically-controlled emission with UV-light enhancing the Coulomb interaction between the electrons and holes resulting in giant enhancement of molecular conductance. The best mechano-optoelectronic switching occurs in the most concave architecture that reduces ambient single-molecule conformational entropy creating artificially-tightened supramolecular assemblies. The performance can be further improved to achieve ultra-high switching ratio on the order of 105 using tetraphenylethylene derivatives with more AIE-active sites. Our results promise new applications from optimized interplay between mechanical force and optics in soft electronics.

The Influence of Technological Factors and Polar Molecules on the Structure of Fibrillar Matrices Based on Ultrafine Poly-3-hydroxybutyrate Fibers Obtained via Electrospinning

The article examines the regularities of structure formation of ultrafine fibers based on poly-3-hydroxybutyrat under the influence of technological (electrical conductivity, viscosity), molecular (molecular weight), and external factors (low-molecular and nanodispersed substances of different chemical natures). Systems with polar substances are characterized by the presence of intermolecular interactions and the formation of a more perfect crystalline fiber structure. Changes in technological and molecular characteristics affect the fiber formation process, resulting in alterations in the morphology of the nonwoven fabric, fiber geometry, and supramolecular fiber structure. Polymer molecular weight, electrical conductivity, and solution viscosity influence fiber formation and fiber diameter. The fiber structure is heterogeneous, consisting of both crystalline and non-equilibrium amorphous phases. This article shows that with an increase in the molecular weight and concentration of the polymer, the diameter of the fiber increases. At the same time, the increase in the productivity of the electrospinning process does not affect the fiber geometry. The chemical structure of the solvent and the concentration of polar substances play a decisive role in the formation of fibers of even geometry. As the polarity of the solvent increases, the intermolecular interaction with the polar groups of poly-3-hydroxybutyrate increases. As a result of this interaction, the crystallites are improved, and the amorphous phase of the polymer is compacted. The action of polar molecules on the polymer is similar to the action of polar nanoparticles. They increase crystallinity via a nucleation mechanism. This is significant in the development of matrix-fibrillar systems for drug delivery, bioactive substances, antiseptics, tissue engineering constructs, tissue engineering scaffolds, artificial biodegradable implants, sorbents, and other applications.

Dual function of new Nd(III) and Gd(III) complexes for cytotoxic and optoelectronic fields: Synthesis, characterization, DFT calculations, and PVA composite films

New two lanthanide complexes of Neodymium (III) and Gadolinium (III) ions were prepared based on 2‐Cyano‐N′‐([4‐oxo‐4H‐chromen‐3‐yl]methylene) acetohydrazide as a chelating agent. The prepared Nd(III) and Gd(III) complexes were characterized via elemental analysis, molecular conductance, IR, and TGA. The obtained results showed the chelating agent behaves as tridentate via oxygen of γ pyrone and carbonyl groups and nitrogen of the azomethine group. The antitumor activity of isolated complexes was investigated against the Ehrlich Ascites Carcinoma cell line (E.A.C). The results of antitumor activity cleared that Gd(III) complex has higher activity than Nd(III) complex and moderate activity relative to cisplatin and 5‐Furacil. Besides, DFT calculations were estimated for prepared Nd(III) and Gd(III) complexes by the Gaussian program. Theoretical parameters were calculated. The energy gap values confirmed the higher activity of the Gd(III) complex over the other Nd(III) complex. In addition, the composite films of Nd(III) and Gd(III) complexes were prepared using the cast technique. The electrical and optical absorption properties of these polymer composites were analyzed.

Phase-Coherent Charge Transport through a Porphyrin Nanoribbon.

Since the early days of quantum mechanics, it has been known that electrons behave simultaneously as particles and waves, and now quantum electronic devices can harness this duality. When devices are shrunk to the molecular scale, it is unclear under what conditions does electron transmission remain phase-coherent, as molecules are usually treated as either scattering or redox centers, without considering the wave-particle duality of the charge carrier. Here, we demonstrate that electron transmission remains phase-coherent in molecular porphyrin nanoribbons connected to graphene electrodes. The devices act as graphene Fabry-Pérot interferometers and allow for direct probing of the transport mechanisms throughout several regimes. Through electrostatic gating, we observe electronic interference fringes in transmission that are strongly correlated to molecular conductance across multiple oxidation states. These results demonstrate a platform for the use of interferometric effects in single-molecule junctions, opening up new avenues for studying quantum coherence in molecular electronic and spintronic devices.

Investigation of the heat transfer enhancement and deterioration induced by vortex generators in low Prandtl number sodium-potassium alloy liquid

Liquid metals, being characterized by low molecular viscosity and high molecular thermal conductivity, appear to be a stupendous choice for heat transfer fluids in deep-space nuclear reactors. Nevertheless, because of space nuclear reactor weight and volume constraints, the heat transfer capability of the heat exchanger must be substantially improved for a deeper space exploration mission. In this study, the influence of the vortex generator applied to the liquid metal was investigated to further promote the heat transfer capability of the liquid metal. And the thermo-fluid behaviors of the sodium-potassium alloy (NaK-78) are compared among the channel with the Body-Centered Cubic (BCC) lattice array, the rectangular ring rib array, and the Kagome lattice array under identical porosity. The numerical results indicate that the heat transfer deterioration phenomena occurred in the case of rectangular ring rib channel, which is a relatively rare occurrence in conventional fluids with the local Nu number even being lower than that of the smooth channel at the same location. Therefore, the rectangular ring rib should be carefully considered and evaluated when it is applied to heat transfer enhancement in NaK alloy fluid. The Kagome structure and the BCC structure could effectively promote the heat transfer performance of the NaK alloy fluid by means of the induced composite vortex system. In comparison to the smooth channel, the average Nu of the cases with the Kagome array and the BCC array yield 17.26–37.32% and 51.98–78.85% higher, respectively.

Ladder-type conjugated molecules as robust multi-state single-molecule switches

•Synthesis of a methylthio-functionalized, ladder-type oligoaniline derivative •Excellent stability and high molecular conductance in oxidized and protonated states •Robust switching of single-molecule conductance among three different states Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches. Ladder-type molecular structures greatly enhance the chemical stability of oligoaniline derivatives and impart well-defined physical properties to multiple molecular charge states. In this work, we characterize the charge transport properties of a ladder-type cyclohexadiene-1,4-diimine derivative at various protonation, lithiation, and oxidation states using single-molecule techniques. Our results show that a ladder-type oligoaniline derivative serves as a robust and reversible molecular switch with over two orders of magnitude changes in molecular conductance when controlled using chemical or electrochemical stimuli. Experimental results are complemented by molecular modeling using density functional theory (DFT) and nonequilibrium Green’s function-DFT (NEGF-DFT) to elucidate charge transport mechanisms at different molecular states. Overall, this work provides new strategies for advancing the stability, programmability, and efficiency of molecular charge transport using ladder-type single-molecule switches.

Contrasting current and future surface melt rates on the ice sheets of Greenland and Antarctica: Lessons from in situ observations and climate models

Surface meltwater production impacts the mass balance of the Greenland and Antarctic ice sheets in several ways, both directly (e.g., through runoff in Greenland) and indirectly (e.g., through cryo-hydrologic warming and frontal melt of marine-terminating glaciers in Greenland and hydrofracturing of ice shelves in Antarctica). Despite its importance, the spatial and temporal patterns in melt rates on both ice sheets are still relatively poorly understood. In this contribution we review and contrast surface melt ‘weather ‘(i.e., short term, intra- and interdiurnal variability) and surface melt ‘climate’ (i.e., longer term, interannual variability and future melt) of both ice sheets. We find that in situ observations using suitably equipped (automatic or staffed) weather stations are invaluable for a complete understanding of the melt process, which represents the complex transport of energy by radiation, turbulence, and molecular conduction between the lower atmosphere, the ice/snow surface, and the subsurface ice/snow layers. We provide example time series of ice sheet melt ‘weather’ for the marginal Greenland ice sheet, where warm and humid air masses tend to increase surface melt rate, and for coastal East Antarctica, where the opposite happens. Apart from process understanding, these in situ observations, which especially in Antarctica are scarce in space and time, are also invaluable to validate, evaluate and calibrate satellite- and model-based estimates of ice sheet surface melt rate. We provide examples of modelled melt maps for both ice sheets, and melt projections for a high-warming, fossil-fuelled development scenario. Although important milestones in melt observations (both in-situ and remotely sensed) and melt models (both global and regional) have recently been reached, we identify multiple outstanding research questions pertaining to current and future ice sheet surface melt rates.

Molecular Weight Segregation and Thermal Conductivity of Polydisperse Wax-Graphene Nanocomposites.

Paraffin waxes are a promising material for heat storage with high energy density. Their low thermal conductivity, which limits the speed of charging and discharging in heat buffers, was previously shown to be improved by adding graphene nanofillers. In the present study, using molecular dynamics simulations, the segregation by molecular weight of polydisperse paraffin near graphene flakes is investigated. In liquid bidisperse paraffin composed of decane and triacontane, an aligned layer containing mainly triacontane was observed next to the graphene. Upon slow cooling, the wax crystallised into distinct layers parallel to the graphene sheet, with much stronger segregation by molecular weight than in the crystallised bidisperse wax without graphene. For polydisperse wax, the segregation effect was much less pronounced. The molten paraffin had a somewhat higher concentration of the longest chains in the first layers next to the graphene, but during crystallisation, the molecular weight segregation was only slightly increased. Measurements of crystallinity using an alternative version of the method developed by Yamamoto showed that the layers of wax were highly aligned parallel to the graphene, both in the solid state with all wax crystallised and in the liquid state with one layer of aligned wax above and below the graphene. Thermal conductivity was increased in planes parallel to the graphene flakes. The strong segregation of chain lengths in the bidisperse wax resulted in clear differences in thermal conductivity in the segregated regions. The less segregated polydisperse wax showed less variation in thermal conductivity.

Electron hopping heat transport in molecules.

The realization of single-molecule thermal conductance measurements has driven the need for theoretical tools to describe conduction processes that occur over atomistic length scales. In macroscale systems, the principle that is typically used to understand thermal conductivity is Fourier's law. At molecular length scales, however, deviations from Fourier's law are common in part because microscale thermal transport properties typically depend on the complex interplay between multiple heat conduction mechanisms. Here, the thermal transport properties that arise from electron transfer across a thermal gradient in a molecular conduction junction are examined theoretically. We illustrate how transport in a model junction is affected by varying the electronic structure and length of the molecular bridge in the junction as well as the strength of the coupling between the bridge and its surrounding environment. Three findings are of note: First, the transport properties can vary significantly depending on the characteristics of the molecular bridge and its environment; second, the system's thermal conductance commonly deviates from Fourier's law; and third, in properly engineered systems, the magnitude of electron hopping thermal conductance is similar to what has been measured in single-molecule devices.

The Electronic Properties of Cadmium Naphthalene Diimide Coordination Complex.

The computational simulations for electronic properties of cadmium (Cd) coordinated L-alanine NDI ligand (H2-l-ala NDI) based complex are the focus of this research. For the first time, the Cd-NDI complex (monomer) has been produced using water as the solvent; this is a new approach to synthesizing the Cd-NDI complex that has not been reported yet. Along with crystallography and Hirsch field analysis, CAM-B3LYP/LANL2DZ and B3LYP/LANL2MB basis sets were used, and in-depth characterisation of the Cd-NDI complex by following DFT and TD-DFT hypothetical simulations. Hyperpolarizabilities, frontier molecular orbitals (FMOs), the density of states (DOS), dipole moment (µ), electron density distribution map (EDDM), transition density matrix (TDM), molecular electrostatic potential (MEP), electron-hole analysis (EHA), and electrical conductivity (σ) have all been studied regarding the Cd-NDI complex. The vibrational frequencies and types of interaction are studied using infrared (IR) and non-covalent interaction (NCI) analysis with iso-surface. In comparison to the Cd-NDI complex with 2.61, 2.42 eV Eg (using CAM-B3LYP/LANL2DZ and B3LYP/LANL2MB basis sets, respectively) and 376 nm λmax, (in case of B3LYP/LANL2MB λmax is higher), H2-l-ala NDI have 3.387 eV Eg and 375 nm λmax, metal-ligand coordination in complex dramatically altered charge transfer properties, such as narrowing band gap (Eg). Based on the electronic properties analysis of Cd-NDI complex, it is predicted that the Cd-NDI complex will have a spectacular (nonlinear optical) NLO response. The Cd-NDI complex is discovered to be advantageous for the creation of future nanoscale devices due to the harmony between the Cd metal and H2-l-ala NDI, in addition to their influences on NLO characteristics.

Potential differentiation of successive SARS-CoV-2 mutations by RNA: DNA hybrid analyses

The constant mutation of SARS-CoV-2 has triggered a new round of public health crises and has had a huge impact on existing vaccines and diagnostic tools. It is essential to develop a new flexible method to distinguish mutations to prevent the spread of the virus. In this work, we used the combination of density functional theory (DFT) and non-equilibrium Green's function formulation with decoherence, to theoretically study the effect of viral mutation on charge transport properties of viral nucleic acid molecules. We found that all mutation of SARS-CoV-2 on spike protein was accompanied by the change of gene sequence conductance, this is attributed to the change of nucleic acid molecular energy level caused by mutation. Among them, the mutations L18F, P26S, and T1027I caused the largest conductance change after mutation. This provides a theoretical possibility for detecting virus mutation based on the change of molecular conductance of virus nucleic acid.

Synthesis, spectroscopic characterization and solid-state electrical behavior of [Ni(L)2] [L = 1,2-di(4-methoxyphenyl)ethene-1,2-dithiolate]: a computational investigation on UV–vis-NIR absorption and electrical transport

A bis(dithiolene)nickel(II) complex, [Ni(L)2] (1) [L = 1,2-di(4-methoxyphenyl)ethene-1,2-dithiolate], has been synthesized and characterized using elemental analysis, UV–vis-NIR, IR, NMR spectroscopies and high resolution mass spectrometry. The geometry of the molecule was optimized using density functional theory (DFT) calculations. The calculated bond angles and distances are in agreement with the literature value. As for other dithiolenes, the present molecule absorbs extensively at 925 nm, in the near-infrared (NIR) region. A time-dependent density functional theory (TD-DFT) predicts the absorption at 1002 nm. The other absorptions are in better parity with the experimental values. In solid-state, 1 conducts electricity. The electrical conductivity of 1 rises on increasing temperature. Upon incremental changes of temperature to 200 °C, the solid-state electrical conductivity of 1 reaches 1.91 × 10−4 S/m. From electrical conductivity versus temperature plot, it is clearly found out that 1 behaves like a semiconductor. The band gap of the molecule was calculated using DFT. The calculated band gap for 1 is 0.0724922 eV which indicates that 1 deviates from metallic to semiconductor-like behavior. The thermal stability of the molecule reveals that the molecule is thermally stable to 200 °C. This is why the temperature variance of the molecular electrical conductivity was measured to this temperature.

Perylene Diimide (PDI) based Flexible Multifunctional Sensor Design for Personal Healthcare Monitoring‐ A Complementary Approach Involving Experimental and Theoretical Investigations

AbstractThis work demonstrates the Perylene Diimide (PDI) based multifunctional sensor for breath‐sensing and Geriatric Emergency Signalling applications fabricated by an economically viable vacuum filtration deposition technique. The deposition of PDI molecules on the flexible substrate forms a moderately conducting percolating molecular network, exhibiting superior pressure and breath‐sensing performance. The pressure sensor displays a sensitivity of 2.42198 kPa−1 with response and recovery times of ≈191 and ≈166 msec. Also, the sensor displays response and recovery times of ≈211 msec and ≈2.651 sec for breath sensing. The durability of the sensor is evaluated using a pressure‐tapping machine, and the sensor displayed a negligible performance drop over ≈10 000 cycles. The experimental findings are complemented by an ab‐initio calculation‐based comprehensive theoretical analysis of the underlying transduction mechanism for pressure and breath sensing in the context of the percolating molecular network. The theoretical analysis reveals that applied pressure and molecular adsorption significantly influence the molecular conductivity as well as the inter‐molecular quantum mechanical tunneling component, which primarily contributes to the observed increase in conductivity with pressure and exposure to breath. An Android/iOS application is developed to wirelessly receive data via Bluetooth from the sensors connected to a microcontroller.

Lyotropic Liquid Crystalline Property and Organized Structure in High Proton-Conductive Sulfonated Semialicyclic Oligoimide Thin Films.

Fully aromatic sulfonated polyimides with a rigid backbone can form lamellar structures under humidified conditions, thereby facilitating the transmission of protons in ionomers. Herein, we synthesized a new sulfonated semialicyclic oligoimide composed of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) and 3,3'-bis-(sulfopropoxy)-4,4'-diaminobiphenyl to investigate the influence of molecular organized structure and proton conductivity with lower molecular weight. The weight-average molecular weight (M w) determined by gel permeation chromatography was 9300. Humidity-controlled grazing incidence X-ray scattering revealed that one scattering was observed in the out-of-plane direction and showed that the scattering position shifted to a lower angle as the humidity increased. A loosely packed lamellar structure was formed by lyotropic liquid crystalline properties. Although the ch-pack aggregation of the present oligomer was reduced by substitution to the semialicyclic CPDA from the aromatic backbone, the formation of a distinct organized structure in the oligomeric form was observed because of the linear conformational backbone. This report is the first-time observation of the lamellar structure in such a low-molecular-weight oligoimide thin film. The thin film exhibited a high conductivity of 0.2 (±0.01) S cm-1 under 298 K and 95% relative humidity, which is the highest value compared to the other reported sulfonated polyimide thin films with comparable molecular weight.

Alpha tensor and dynamo excitation in turbulent fluids with anisotropic conductivity fluctuations

AbstractA mean‐field theory of the electrodynamics of a turbulent fluid is formulated under the assumption that the molecular electric conductivity is correlated with the turbulent velocity fluctuation in the (radial) direction, . It is shown that for such homogeneous fluids a strong turbulence‐induced field advection anti‐parallel to arises almost independently of rotation. For rotating fluids, an extra effect appears with the known symmetries and with the expected maximum at the poles. Fast rotation, however, with Coriolis number exceeding unity suppresses this term. Numerical simulations of forced turbulence using the nirvana code demonstrate that the radial advection velocity, , always dominates the term. We show finally with simplified models that dynamos are strongly influenced by the radial pumping: for the solutions become oscillatory, while for they become highly exotic if they exist at all. In conclusion, dynamo models for slow and fast solid‐body rotation on the basis of finite conductivity–velocity correlations are unlikely to work, at least for dynamos without strong shear.