Search

A method for the calculation of divergenceless, magnetically induced quantum mechanical current densities in molecules that approximates the exact current is presented. This was achieved by adding to the calculated conventional current density, i.e., a current that typically has a non-zero divergence, a corrective term that is the negative of the irrotational field of its Helmholtz decomposition. The solenoidal field of the decomposition is the divergence-free current density, which is still an approximation of the exact current but which now satisfies the continuity requirement regardless of the quality of the basis set. Based on calculations performed on several simple molecules (LiH, H2O, benzene, and zethrene), adopting different kinds of low-level theoretical approaches, clear improvements are observed in the correspondence of vortices, sources, and sinks for which the conventional current density shows a lack of continuity. A little improvement is also observed for the calculated diagonal components of the magnetizability tensor. [ABSTRACT FROM AUTHOR]

We investigate the numerical accuracy of the extended Koopmans's theorem (EKT) in reproducing the full configuration interaction (FCI) and complete active-space configuration interaction (CAS-CI) ionization energies (IEs) of atomic and molecular systems calculated as the difference between the energies of N and (N − 1) electron states. In particular, we study the convergence of the EKT IEs to their exact values as the basis set and the active space sizes vary. We find that the first FCI EKT IEs approach their exact counterparts as the basis set size increases. However, increasing the basis set or the active space sizes does not always lead to more accurate CAS-CI EKT IEs. Our investigation supports the observation of Davidson et al. [J. Chem. Phys. 155, 051102 (2021)] that the FCI EKT IEs can be systematically improved with arbitrary numerical accuracy by supplementing the basis set with diffuse functions of appropriate symmetry, which allow the detached electron to travel far away from the reference system. By changing the exponent and the center of the diffuse functions, our results delineate a complex pattern for the CAS-CI EKT IE of LiH, which can be important for the spectroscopic studies of small molecules. [ABSTRACT FROM AUTHOR]

We present a robust strategy to numerically sample the Coulomb potential in reciprocal space for periodic Born–von Karman cells of general shape. Our approach tackles two common issues of plane-wave based implementations of Coulomb integrals under periodic boundary conditions: the treatment of the singularity at the Brillouin-zone center and discretization errors, which can cause severe convergence problems in anisotropic cells, necessary for the calculation of low-dimensional systems. We apply our strategy to the Hartree–Fock and coupled cluster (CC) theories and discuss the consequences of different sampling strategies on different theories. We show that sampling the Coulomb potential via the widely used probe-charge Ewald method is unsuitable for CC calculations in anisotropic cells. To demonstrate the applicability of our developed approach, we study two representative, low-dimensional use cases: the infinite carbon chain, for which we report the first periodic CCSD(T) potential energy surface, and a surface slab of lithium hydride, for which we demonstrate the impact of different sampling strategies for calculating surface energies. We find that our Coulomb sampling strategy serves as a vital solution, addressing the critical need for improved accuracy in plane-wave based CC calculations for low-dimensional systems. [ABSTRACT FROM AUTHOR]

Lithium foils were demonstrated to absorb surrogate protium for tritium-powered betavoltaics. 20 μ m thick lithium foils were hole-punched from a ribbon of electrodeposited lithium on copper foil. The lithium foils were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and at all loading temperatures above the lithium melting point at 190, 200, 225, 250, and 300. Lithium hydride formation was confirmed with Raman spectroscopy after hydrogen loading. The kinetics of experimental hydride formation was compared to the diffusion-limited Mintz–Bloch model. While the Mintz–Bloch model showed good fit with the experimental loadings, the model overpredicted the loading kinetics starting at 250 °C and at higher temperatures. The overprediction was either caused by lithium hydride outgassing due to some reduction with some residual lithium hydroxide created from brief air exposure when sealing the lithium in the reactor or a transition from diffusion-limited hydride growth to surface or metal–hydride interface-limited hydride growth. [ABSTRACT FROM AUTHOR]

To describe the four fundamental interactions observed in the universe, we used the Dirac equation containing an interaction of the screened Kratzer and the Hulthen potential with a ring-shaped term. We study the energy spectra of spin- 1 / 2 particles in noncompact extra dimensions. The polar and angular parts of the N-dimensional Dirac equation are solved using the Nikiforov–Uvarov method. The transcendental energy equation and the associated two components spinor wavefunctions of the spin- 1 / 2 particles are obtained. Moreover, we obtained the nonrelativistic limit of our results by mean of a specific mapping. Some special cases of the proposed potential have been discussed, and their corresponding eigenvalue energies were determined. Finally, we proposed that our results can be used in many branches of physics, to investigate scenarios in extra dimensions where spin- 1 / 2 particles are involved. To test the reliability of our model, we computed the numerical values of the energy spectra of lithium hydride and hydrogen chloride diatomic molecules using a special case of the proposed potential. The energy spectra are calculated for different quantum numbers (n , l) at different values of the dimensionality of the space. The results of this research are overall in good agreement with the theoretical studies of similar investigation. [ABSTRACT FROM AUTHOR]

Dense lithium hydride (LiH) is widely used in neutron shielding applications for thermonuclear reactors and space systems due to its unique properties. However, traditional sintering methods often lead to cracking in LiH products. This study investigates the densification sintering of LiH using microwave technology. A multiphysics model was established based on the measured dielectric properties of LiH at different temperatures, allowing for a detailed analysis of the electromagnetic and thermal field distributions during the microwave heating of cylindrical LiH samples. The results indicate that the electric field distribution within the LiH is relatively uniform, with resistive losses concentrated primarily in the LiH region of the microwave cavity. LiH rapidly absorbs microwave energy, reaching the sintering temperature of 520 °C in just 415 s. Additionally, the temperature difference between the low- and high-temperature regions during the sintering process remains below 5 °C, demonstrating excellent uniform heating characteristics. The microwave sintering process enhances interface migration within the LiH samples, resulting in dense metallurgical bonding between grains. In summary, this research provides valuable insights and theoretical support for the rapid densification of LiH materials, highlighting the potential of microwave technology in improving material properties. [ABSTRACT FROM AUTHOR]

The damage mechanism and fracture behavior of lithium hydride (LiH) ceramic are key to its design and application at elevated temperature in nuclear engineering. LiH ceramic is tested in a loading rate range of 0.001–2 mm/min from room temperature (RT) to 600 °C using digital image correlation (DIC) method combined with high-speed photography. At low temperature (up to 300 °C), LiH ceramic undergoes brittle fracture. At high temperature (up to 600 °C), LiH ceramic undergoes creep fracture at low loading rate and ductile fracture at high loading rate. The main crack growth rate of LiH ceramic with ductile fracture is higher than that of LiH ceramic with creep fracture, and is lower than that of LiH ceramic with brittle fracture. With the change of temperature and loading rate, three damage mechanisms, fatigue damage corresponding to SCG of inherent flaws, creep damage represented by creep microcracks and ductile damage symbolled by dimples, occur simultaneously and show competitive characteristics, one of which dominates the failure. At low loading rate, there is a transition of the dominant damage mechanism from fatigue to creep damage with increasing temperature. At high temperature, the dominant damage mechanism changes from creep to ductile damage with the increase of loading rate. [ABSTRACT FROM AUTHOR]

As a highly promising next‐generation high‐specific capacity anode, the industrial‐scale utilization of micron silicon has been hindered by the issue of pulverization during cycling. Although numerous studies have demonstrated the effectiveness of regulating the inorganic components of the solid electrolyte interphase (SEI) in improving pulverization, the evolution of most key inorganic components in the SEI and their correlation with silicon failure mechanisms remain ambiguous. This study provides a clear and direct correlation between the lithium hydride (LiH) in the SEI and the degree of micron silicon pulverization in the battery system. The reverse lithiation behavior of LiH on micron silicon during de‐lithiation exacerbates the localized stress in silicon particles and contributes to particle pulverization. This work successfully proposes a novel approach to decouple the SEI from electrochemical performance, which can be significant to decipher the evolution of critical SEI components at varied battery anode interfaces and analyze their corresponding failure mechanisms. [ABSTRACT FROM AUTHOR]

Lithium compounds such as lithium hydride (LiH) and lithium hydroxide (LiOH) have a wide range of industrial applications, but are highly reactive in environments with H2O and CO2. These reactions lead to the ingrowth of secondary lithium compounds, which can alter the homogeneity and affect the application of particular lithium chemicals. This study performed an exploratory analysis of different lithium compounds using laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy. Machine learning models are trained on the recorded spectral data to discriminate emission features that differ between LiH, LiOH, and Li2CO3 to perform high-fidelity classification. Support vector machine classifiers yield perfect prediction accuracy between the three compounds with optimal training time. Multivariate methods are then used to produce regression models quantifying the ingrowth of LiOH in LiH. Performing a mid-level data fusion of selected LIBS and Raman features with partial least-squares regression produces the superlative model with a root mean square error of 2.5 wt % and a detection limit of 6.3 wt %. [ABSTRACT FROM AUTHOR]

Lithium hydride (LiH) is a promising material for the production of hydrogen via hydrolysis. However, the formation of lithium hydroxide (LiOH) during the hydrolysis process hinders contact between the remaining LiH and water, retarding the hydrolysis reaction and increasing the actual amount of water required. Through this study, it is demonstrated that an increase in the hydrogen ion concentration can improve the hydrolysis of LiH. When the hydrogen ion concentration reaches 1 mol L−1, the maximum hydrolysis rate is 232.6 mL min−1, and the H 2 generation yield reaches 2102.8 mL. Additionally, we investigated the effects of doping solid acids and strong acid–weak base salts on LiH hydrolysis. Experimental results indicate that the addition of solid acids led to a hydrogen generation behavior similar to that with acid solutions. In particular, after the addition of oxalic acid, the maximum hydrolysis rate attained was 362.0 mL min−1, and the H 2 generation yield reached 2108.3 mL. After the addition of dl -malic acid, citric acid and dl -tartaric acid, the maximum hydrolysis rate attained were 173.1, 170.0 and 255.8 mL min−1, respectively. Under alkaline conditions, the hydrolysis of strong acid–weak base salts was enhanced, and the released hydrogen ions consumed LiOH, thereby increasing the rate of LiH hydrolysis. After the addition of CuSO 4 , the maximum hydrolysis rate attained was 403.8 mL min−1, and the H 2 generation yield attaining 2036.0 mL. After the addition of AlCl 3 and FeCl 3 , the maximum hydrolysis rate attained were 212.5 and 221.3 mL min−1. Thus, an increase in the concentration of hydrogen ions and the addition of solid acids and strong acid–weak base salts are effective techniques for reducing the adverse effects of LiOH formation on LiH hydrolysis for hydrogen production. [Display omitted] • Methods to mitigate the impact of LiOH on LiH hydrolysis are researched. • The addition of solid acids and strong acid-weak base salts enhance the hydrolysis rate of LiH. • The addition of CuSO 4 resulted in the maximum hydrolysis rate reaching 403.8 mL min−1. [ABSTRACT FROM AUTHOR]

This research comprehensively addressed various aspects of hydrogen storage, with a focus on metallic hydride materials, lithium hydride LiH, one of the lightest reversible metal hydrides, boasts a remarkable gravimetric density of up to 12.67 wt% and an impressive volumetric capacity of 4.95 Kg/100 L. Despite these strengths, challenges accompany lithium hydride, such as its elevated formation energy and a high desorption temperature around 600 K–700 K. In this work, ab initio calculations based on Density Functional Theory (DFT) were used to study the thermodynamic and electronic properties of this material with the aim of reducing the high temperature of decomposition while preserving a significant gravimetric capacity and satisfactory stability in line with the U.S. Department of Energy (DOE) standards for solid-state hydrogen storage (ΔH f = - 40 kJ/mol.H 2 and T d = 289 K–393 K). The results obtained show the influence of the doping effect firstly (Li 1-x F x H, Li 1-x N x H) on the improvement of the hydrogen storage properties, with a percentage gain of 50.64% for 4% doping with F and 49.08% for 8% doping with N. Secondly, a 38.63% gain in thermodynamic stability was observed by applying triaxial compressive stresses to the LiH compound. • 4% of fluorine doping in LiH reduces the enthalpy of formation to −39.45 kJ/molH 2 and T d to 301.83 K. • 8% nitrogen doping in LiH decreases formation enthalpy to −41.09 kJ/mol H 2 and T d to 314.38 K. • -12% triaxial compressive strain decreases the formation enthalpy to −49.49 kJ/molH 2 and T d to 378.65 K. [ABSTRACT FROM AUTHOR]

We introduce two different approaches to represent the second-quantized electronic Hamiltonian in a sum-of-products form. These procedures aim at mitigating the quartic scaling of the number of terms in the Hamiltonian with respect to the number of spin orbitals and thus enable applications to larger molecular systems. Here, we describe the application of these approaches within the multi-configuration time-dependent Hartree framework. This approach is applied to the calculation of eigenenergies of LiH and electronic ionization spectrum of H2O. [ABSTRACT FROM AUTHOR]

We present a Kohn–Sham (KS) inversion approach to construct KS exchange–correlation potentials corresponding to given electron densities. This method is based on an iterative procedure using linear response to update potentials. All involved quantities, i.e., orbitals, potentials, and response functions, are represented by Gaussian basis functions. In contrast to previous KS inversion methods relying on Gaussian basis sets, the method presented here is numerically stable even for standard basis sets from basis set libraries due to a preprocessing of the auxiliary basis used to represent an exchange–correlation charge density that generates the exchange–correlation potential. The new KS inversion method is applied to reference densities of various atoms and molecules obtained by full configuration interaction or CCSD(T) (coupled cluster singles doubles perturbative triples). The considered examples encompass cases known to be difficult, such as stretched hydrogen or lithium hydride molecules or the beryllium isoelectronic series. For the stretched hydrogen molecule, potentials of benchmark quality are obtained by employing large basis sets. For the carbon monoxide molecule, we show that the correlation potential from the random phase approximation (RPA) is in excellent qualitative and quantitative agreement with the correlation potential from the KS inversion of a CCSD(T) reference density. This indicates that RPA correlation potentials, in contrast to those from semi-local density-functionals, resemble the exact correlation potential. Besides providing exchange–correlation potentials for benchmark purposes, the proposed KS inversion method may be used in density-partition-based quantum embedding and in subsystem density-functional methods because it combines numerical stability with computational efficiency. [ABSTRACT FROM AUTHOR]

The electronic current density, induced in a molecule by the optical magnetic field associated with a frequency-dependent monochromatic plane wave, assumed to be spatially uniform within the electric quadrupole approximation, has been studied by using a theoretical method based on a continuous translation of its origin. The induced electronic current density vector field designated by this procedure, invariant of the origin for any point of the molecular domain, is obtained via a computational scheme, formally annihilating the diamagnetic contribution of the conventional common-origin approach based on perturbation theory. In a preliminary application of the theoretical methods outlined in the present work, the simple molecule of lithium hydride has been investigated. Particular attention has been paid to the structure of induced electronic current density for several values of the magnetic field frequency by investigating equilibrium points of four different types, organized in stagnation lines, which constitute its stagnation graph, i.e., a topological fingerprint of the vector field conveying complete information in the condensed form, to verify the fulfillment of fundamental requirements, e.g., the continuity equation and the Poincaré–Hopf theorem on spherical and toroidal surfaces. [ABSTRACT FROM AUTHOR]

Due to its lightweight and strong neutron shielding, lithium hydride (LiH) is a potential candidate shielding material in small modular reactors (SMR). However, the preparation of large-sized, thick-walled lithium hydride blocks using conventional methods faces challenges such as slow ramp-up rates, excessive grain growth, and large temperature gradients, and microwave sintering technology may offer a good solution to the above problems. The material's dielectric spectrum properties and thermal conductivity parameters were evaluated using first principles calculations, which may serve as a reference for exploring the lithium hydride microwave sintering mechanism. The static dielectric constant of lithium hydride was 4.4 and the optical dielectric constant was 1. The thermal conductivity at 300 K was 15.88 (W m−1 k−1), which was consistent with the existing experimental value of 14.7 (W m−1 k−1). Furthermore, we discussed the effect of temperature and vacancy defects on the dielectric temperature spectral properties of the material. The results showed that while the thermal conductivity decreased with increasing temperature, and the phonon thermal conductivity of LiH (vacancy defects) decreased. The presence of a vacancy defect in LiH leads to an increase in the number of free electrons near the Fermi level, thereby enhancing its electron thermal conductivity. The optimal sintering frequency of LiH with vacancy defects also decreased. [Display omitted] • The dielectric temperature characteristics of the material resolved the sintering effect. • Thermal conductivity could be accurately evaluated by considering heat expansion. • Vacancy defects (VD) could improve the thermal conductivity of LiH. • VD reduced the frequency range of dielectric dissipation and increased the EELS. • This study could serve as a reference for determining the external electromagnetic field frequency. [ABSTRACT FROM AUTHOR]

LiH is valued by researchers and engineers for its high-temperature resistance, high strength, high hydrogen storage capacity of up to 12.6 wt%, and high neutron absorption cross section. However, sintering and application of this material are difficult. Lithium hydride is a highly effective neutron shielding material. The neutron shielding ability of lithium hydride is directly affected by the homogeneity of the total amount and distribution of hydrogen. The heat migration of hydrogen reduces the neutron shielding effectiveness of lithium hydride. It is critical to forecast H's diffusion behavior. The diffusion coefficient is a critical metric for determining the diffusion efficiency. As a result, the stability, electronic structure, and bonding properties of LiH, LiOH, and H entering the tetrahedral interstitial sites of LiH were calculated using first principles based on density functional theory (DFT). The elastic modulus of the system was also examined to find the lowest thermal conductivity, and some thermodynamic parameters were derived by calculating LiH phonons. Finally, static calculations were used to determine the diffusion coefficient and diffusion activation energy of H in the LiH solid solution. The results revealed that the addition of H altered the characteristics of the LiH semiconductor, giving it metallic features. The lowest thermal conductivity of the LiH system was 2.9. W·m−1 K−1. The diffusion coefficient was D = (2.638 × 10 − 2 c m 2 / s ) exp ( − 5.811 × 10 − 3 cal / K B T). The activation energy for diffusion was 0.252 eV. The diffusion coefficients, elastic constants, and lattice parameters all corresponded well with previously published results. The density functional theory was employed to study the material's system energy and electrical structure, and the microscopic migratory behavior of hydrogen was predicted theoretically. The calculation of the lowest thermal conductivity provided a reference for the screening of ceramic materials. • First-principles calculations can allow for a better understanding of the H diffusion mechanism in LiH materials. • Diffusion from the LiH surface to the interior of the material requires greater energy drive. • The introduction of interstitial H atoms can make LiH have metal properties. • The lowest thermal conductivity of the material can provide a reference for the selection of ceramic materials. • LiOH is more thermally stable than LiH. [ABSTRACT FROM AUTHOR]

Regulation of photodissociation dynamics of oriented LiH molecules in different dissociation channels is proposed based on time dependent quantum wave packet theory. The enhancement of molecular orientation on the photodissociation of LiH is obvious with our theoretical scheme. The results show that the molecular orientation in the ground state has a great effect on the angular distributions of wave packets. By using the proper laser pulses and controlling the polarization direction of the laser pulses, the enhancement of the photodissociation could be realized. After the molecular orientation, an optimal dissociation channel is observed with an improved dissociation probability. Compared with the results without molecular orientation, the maximal dissociation probability is increased by 8.1% in the indirect dissociation channel and 30.7% in the direct dissociation channel. The enhancement effect is more obvious in the direct dissociation channel, which provides a possible method to manipulate the dissociation of LiH molecules experimentally. Additionally, the photodissociation process of LiH also relies on the electric intensity and delay time of two pump pulses. [ABSTRACT FROM AUTHOR]

In the present work, we search for the maximum of the functional $ |\langle \Phi ^{\prime }|\hat {H}|\Phi \rangle | $ | ⟨ Φ ′ | H ^ | Φ ⟩ | , where $ |\Phi ^{\prime }\rangle $ | Φ ′ ⟩ is a Slater Determinant (SlDet) and $ \hat {H} $ H ^ is the exact Hamiltonian of an atom or a molecule, starting from a SlDet $ |\Phi \rangle $ | Φ ⟩ , with its spin orbitals calculated by the standard Hartree-Fock (HF) equation or other approximation or any determinant. The element $ |\langle \Phi _{1}|\hat {H}|\Phi \rangle | $ | ⟨ Φ 1 | H ^ | Φ ⟩ | with $ |\Phi _{1}\rangle $ | Φ 1 ⟩ the maximising $ |\Phi ^{\prime }\rangle $ | Φ ′ ⟩ gives a value greater or equal to $ |\langle \Phi |\hat {H}|\Phi \rangle | $ | ⟨ Φ | H ^ | Φ ⟩ | . Next we calculate the corresponding maximum overlap $ |\langle \Phi _{2}|\hat {H}|\Phi _{1}\rangle | $ | ⟨ Φ 2 | H ^ | Φ 1 ⟩ | and finally $ |\langle \Phi _{n+1}|\hat {H}|\Phi _{n}\rangle | $ | ⟨ Φ n + 1 | H ^ | Φ n ⟩ | until $ |\langle \Phi _{n+1}|\hat {H}|\Phi _{n}\rangle -\langle \Phi _{n}|\hat {H}|\Phi _{n-1}\rangle |\leq \varepsilon $ | ⟨ Φ n + 1 | H ^ | Φ n ⟩ − ⟨ Φ n | H ^ | Φ n − 1 ⟩ | ≤ ε , where ε determines the desired numerical accuracy. We show that the sequence $ \langle \Phi _{n+1}|\hat {H}|\Phi _{n}\rangle $ ⟨ Φ n + 1 | H ^ | Φ n ⟩ converges to an extremum $ \langle \Phi |\hat {H}|\Phi \rangle $ ⟨ Φ | H ^ | Φ ⟩. Having found the SlDet with the lowest energy we repeat the procedure in the orthogonal subspace for finding the first and the higher excited states. We applied this method in order to determine the energies of several configurations of H $ _{3} $ 3 , the Lithium atom, LiH and Be. [ABSTRACT FROM AUTHOR]

Lithium hydride (LiH) is an important hydrogen storage, heat storage and neutron shielding material. When used in neutron shielding structure, its size and strength have certain requirements, which would be met by LiH ceramics. However, it fails easily during sintering due to severe thermal stress and high brittleness. In this study, the influences of the dimension, furnace temperature cooling rate, and convection condition on the mechanical behavior were systematically examined. The results indicated that larger dimensions and faster furnace temperature cooling rates resulted in higher maximum stresses. Furthermore, convection was beneficial for reducing the thermal stress. Accordingly, a process-based failure assessment diagram method was proposed to evaluate the safety of LiH ceramics, and a bilinear precise temperature control approach was proposed. Based on this method, the tube thickness was increased by 25 % and the cooling time was reduced by 32 % compared to those using linear temperature control in an example. The conclusion and method could be applied to optimize the temperature control for more practical large-dimension sintering. [ABSTRACT FROM AUTHOR]

Lithium is a popular lightweight material in the field of energy storage because of its hydrogen-binding properties and electrochemical advantages. The high hydrogen uptake capacity (∼12.6 wt%) of lithium hydride (LiH) is limited by the major thermodynamic constraint of requiring a higher temperature (∼700 °C) for desorption at 0.1 MPa. Incorporating a third element that creates Li phases during LiH dehydrogenation can help overcome thermodynamic constraints. This study involves modifying the hydrogen storage properties and thermodynamic characteristics of LiH through mechanical alloying with porous silicon (PS). Pressure composition isotherms measure the reversible hydrogen storage capacity (∼3.39 wt%) of LiH-PS alloy at different temperatures. The energy of hydrogen interaction is quantified by isosteric heat of absorption, which provides the enthalpy change in the reaction system. Hydrogen absorption and desorption enthalpies of 94.5 kJ (mol H 2)−1 and 114.9 kJ (mol H 2)−1 demonstrate the lowest energy demand among previously reported LiH alloys. The energy of hydrogen interaction is quantified by isosteric heat of absorption, which provides the enthalpy change in the reaction system. The hydride decomposition of the alloy indicates the possible range of hydrogen desorption. • Li-PS alloy undergoes a phase transformation enabling reversible hydrogen storage. • The highest hydrogen uptake of 3.39 wt% is observed at 500 °C and 4 MPa. • LiH-PS alloy shows lower absorption enthalpy of ∼94.5 kJ (mol H 2)−1. • The hydrogen reaction enthalpy is reduced by ∼66 kJ (mol H 2)−1 than that of LiH. • Onset hydrogen decomposition energy decreases by ∼6% with LiH-PS than LiH–Si alloy. [ABSTRACT FROM AUTHOR]

The exponential scaling of quantum states results in greater processing costs, making it impossible to simulate complex quantum systems on conventional supercomputers. In order to overcome this obstacle, quantum computers simulate one quantum system using another quantum system. In the current study, a method for simulating basic molecules like LiH that uses the Variational Quantum Technique, a far less computationally expensive algorithm, is used. By selecting a suitable trial function in this case, we also theoretically verify the results and present everything in a very straightforward way. Until we transcend the NISQ constraint of fault-tolerant quantum computers, this approach uses extremely shallow circuits to determine the minimal energy eigenvalue of a molecule. [ABSTRACT FROM AUTHOR]

Phase equilibria involving solid solutions in the Li–Eu–O system in an oxidizing, inert, and reducing atmospheres during annealing mixtures of various precursors subjected to preliminary mechanochemical activation at temperatures of 400–1100°C and partial pressures ~ 21 and 0.01 kPa and ~ 5 kPa have been studied by X-ray powder diffraction and thermogravimetry. The solubility of lithium in EuO has been first estimated, which is no less than 50–60%. For Eu2O3 and , it is 30% of the total amount of cations. Along with LiEuO2, the formation of crystalline mixed-valent (EuII + EuIII) phases LiEu3O4 and Li2Eu5O8 has been confirmed. The thermal behavior of solid solutions Eu1 –xLixO1 – δ based on europium monoxide and Li1 +yEu3O4 – γ in air has been studied. The concentration phase diagram of the Li–Eu–O system has been constructed. [ABSTRACT FROM AUTHOR]

The interaction between protic hydrogen (H+) and hydridic hydrogen (H−) species gives rise to H2 and spawns the establishment of metal‐N−H hydrogen storage material systems. N‐based compounds such as metal amides (M−NH2) have shown viability for protic H generation. In this preliminary research, we adopted a chemical reaction approach using a hydrogen‐enriched quasi‐aromatic tri‐amide "melamine (C3H6N6)" as protic H feedstock and lithium hydride (LiH) as the hydridic H‐based destabilizer aiming at expanding metal and organic substrates and developing new metalorganic hydride materials. The dehydrogenation kinetics and reaction pathways of C3H6N6−xLiH (x=1, 3 or 6) composites on heating and ball‐milling conditions were investigated in detail. The results showed that C3H6N6−LiH consisting of a 1/6 mole ratio can evolve 6.6 wt % H2 (approximately 5.75 equiv. H2) at room temperature through mechanochemical method of ball‐milling. Interestingly, it showed different reaction paths under heating, C3H6N6−6LiH composite could release 2.87 wt % hydrogen under 210 °C and transform into a CN heterocyclic intermediate structure examined by NMR, FTIR, XRD, and Raman characterizations. [ABSTRACT FROM AUTHOR]

Considering the LiH case study, a semi-quantitative approach is presented to locate the energy and interatomic ranges of charge transfer states. Using basis sets of increasing size, it is shown how their effect on the quality of description of neutral and anionic hydrogen can be used to determine the ionic nature of the ground and excited electronic states. The results are satisfactorily compared to those obtained from the permanent dipole moment analysis. [ABSTRACT FROM AUTHOR]

The Germanium (Ge), as a fast‐charging and high specific capacity (1568 mAh g−1) alloy anode, is greatly hampered in practical application by poor cyclability. To date, the understanding of cycling performance degradation remains elusive. This study illustrates that, contrary to conventional beliefs, most of the Ge material in failed anodes still retains good integrity and does not undergo severe pulverization. It is revealed that capacity degradation is clearly correlated to the interfacial evolution of lithium hydride (LiH). Tetralithium germanium hydride (Li4Ge2H), as a new species derived from LiH, is identified as the culprit of Ge anode degradation, which is the dominant crystalized component in an ever‐growing and ever‐insulating interphase. The significantly increased thickness of the solid electrolyte interface (SEI) is accompanied by the accumulation of insulating Li4Ge2H upon cycling, which severely retards the charge transport process and ultimately triggers the anode failure. We believe that the comprehensive understanding of the failure mechanism presented in this study is of great significance to promoting the design and development of alloy anode for the next generation of lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Abstract The reviving of the “Holy Grail” lithium metal batteries (LMBs) is greatly hindered by severe parasitic reactions between Li anode and electrolytes. Herein, first, we comprehensively summarize the failure mechanisms and protection principles of the Li anode. Wherein, despite being in dispute, the formation of lithium hydride (LiH) is demonstrated to be one of the most critical factors for Li anode pulverization. Secondly, we trace the research history of LiH at electrodes of lithium batteries. In LMBs, LiH formation is suggested to be greatly associated with the generation of H2 from Li/electrolyte intrinsic parasitic reactions, and these intrinsic reactions are still not fully understood. Finally, density functional theory calculations reveal that H2 adsorption ability of representative Li anode protective species (such as LiF, Li3N, BN, Li2O, and graphene) is much higher than that of Li and LiH. Therefore, as an important supplement of well‐known lithiophilicity theory/high interfacial energy theory and three key principles (mechanical stability, uniform ion transport, and chemical passivation), we propose that constructing an artificial solid electrolyte interphase layer enriched of components with much higher H2 adsorption ability than Li will serve as an effective principle for Li anode protection. In summary, suppressing formation of LiH and H2 will be very important for cycle life enhancement of practical LMBs.

The LaMg 12 H 27 (LMH) and LMH-5 wt% LiH samples were prepared by different ball milling times, and the hydrogen generation performances of samples were investigated and compared. X-ray diffraction and scanning electron microscopy techniques were adopted to elucidate the performance improvement mechanisms. For the LMH, with the increase of ball milling time, the hydrogen generation yield and kinetics can be improved significantly. This may be caused by the change in particle size and crystallite size of the LMH sample after ball milling. However, for the LMH-5 wt% LiH, with the increase of the ball milling time, the initial kinetics increases firstly, and then decreases. This may be due to the gradual movement of LiH from the surface to the interior of LMH and to the covering of LMH after ball milling. [Display omitted] • The LaMg 12 H 27 –LiH hydrolysis materials were prepared by ball milling. • The highest hydrogen yield reached 1247 mL/g with a conversion rate of 96%. • The hydrolysis mechanism of LaMg 12 H 27 –LiH samples is reported. [ABSTRACT FROM AUTHOR]

A new framework based on density matrix embedding theory (DMET) capable of directly targeting excited electronic states is proposed and implemented. DMET has previously been shown to be an effective method of calculating the ground state energies of systems exhibiting strong static correlation but has never been applied to calculate excited state energies. In this work, the Schmidt decomposition is applied directly on excited states, approximated by higher lying self-consistent field solutions. The DMET prescription is applied following this Schmidt decomposition allowing for a direct embedding of excited states. Initial results are obtained for a system of multiple hydrogen dimers and the lithium hydride dissociation. We analyze the nature of each part of the excited state DMET calculation and identify challenges. These challenges to the implementation of excited state DMET are discussed, and potential suggestions moving forward are recommended. [ABSTRACT FROM AUTHOR]

Alkenes that normally do not react with LiAlH4 (3‐hexene, cyclohexene, 1‐Me‐cyclohexene), can be reduced to the corresponding alkanes by a mixture of LiAlH4 and Fe0 (the iron was activated by Metal‐Vapour‐Synthesis). This alkene‐to‐alkane conversion with a stoichiometric quantity of LiAlH4/Fe0 does not need quenching with water or acids, implying that both H's originate from LiAlH4. The LiAlH4/Fe0 combination is also a remarkably potent cooperative catalyst for hydrogenation of multi‐substituted alkenes and benzene or toluene. An induction period of circa two hours and the minimally required temperature of 120 °C, suggests that the actual catalyst is a combination of Fe0 and the decomposition product of LiAlH4 (LiH and Al0). A thermally pre‐activated LiAlH4/Fe0 catalyst did not need an induction time and is also active at room temperature and 1 bar H2. A combination of AliBu3 and Fe0 is an even more active hydrogenation catalyst. Without pre‐activation, tetra‐substituted alkenes like Me2C=CMe2 and toluene could be fully hydrogenated. [ABSTRACT FROM AUTHOR]

Quantum description of the isothermal and adiabatic magnetocaloric effect (MCE), thermomagnetic properties, and energy spectra of three diatomic molecules, namely: lithium hydride (LiH), titanium hydride (TiH), and scandium hydride (ScH), was examined with Deng-Fan-Screened Coulomb Potential using the Greene-Aldrich approximation to the centrifugal term. The numerical solutions of the proposed potential with and without the magnetic and AB flux fields obtained reveal that the combined impacts of the magnetic and AB flux fields completely remove the degeneracy of the energy spectra and control the behaviour of the MCE by acting as a regulating factor to cool or heat the MCE. Also, the proposed potential reduces to three exceptional cases, and the thermomagnetic plots obtained for the analysed dimer molecules agreed perfectly with previous work. This research has the potential to be applied in molecular physics and MCE studies for a variety of molecules. [ABSTRACT FROM AUTHOR]

An organic solvent-assisted catalyst-free mechanochemical reaction is developed to synthesize lithium hydride at mild gas pressures and room temperature. Studies show that the formation of intermediates on the surface of bulk lithium metal is crucial for the synthesis of high purity (>98%) LiH. This provides a new strategy for the large-scale production of lithium-based hydrogen storage materials. [ABSTRACT FROM AUTHOR]

The single-crystal lithium hydride (LiH) generally grows in a gradient temperature region with the Bridgman method. A stable and appropriate temperature gradient is crucial in the crystallization process. In this paper, the temperature variation of single-crystal LiH growth is calculated by the finite element method (FEM). It is shown that the LiH compact melted entirely after heating to 750 °C at 10 °C/min in a dual-temperature furnace and holding for 2.4 h. The crystallization margin was 46.5 °C after holding for 5 h. The crystallization margin of LiH at the cone point, respectively, decreased to 33.7 °C, 28.6 °C, 25.6 °C, and 16.5 °C when the upper furnace was maintained at 750 °C, and lower furnace was cooled to 680 °C, 650 °C, 630 °C, and 550 °C, respectively. The optimal conditions for obtaining large size and high-quality LiH single crystals were predicted to be 630 °C at a lower-temperature-zone, 200 mL/min (cooling water flux), and 20 mm/h rise rate of the furnace. Based on the parameters of the above simulation, we synthesized LiH single crystal. X-ray diffraction (XRD) patterns showed that the LiH single crystal exhibited a (2 0 0) crystallographic plane at 44.5° with good chemical stability in air. [ABSTRACT FROM AUTHOR]

Using coupled cluster calculations with quadruple-zeta basis sets optimal structures and dissociation energies were obtained for complexes of LiF and LiCl with LiH, HF, HCl, H2, Li2, F2, Cl2, FCl, H2O and NH3. Structures for LiF-LiF and LiCl-LiCl have D2h symmetry, while the structure of LiF-LiCl, as well as structures of LiF and LiCl with LiH, HF and Li2 are cyclic, with C2v symmetry. Most other systems have Cs symmetry, many in near-cyclic form. The largest dissociation energy of 21,304 cm−1 was obtained for LiF-LiF. Dissociation energies for LiCl-LiCl and for cyclic C2v systems range from about 10,000 to 20,000 cm−1. For cyclic systems with D2h and C2v symmetries harmonic vibrational frequencies cannot be related to monomer frequencies. Their higher frequencies, however, are close to frequencies of triatomic Li-Y-Li, with Y = H, F, Cl, and to frequencies of F-H-F-. [ABSTRACT FROM AUTHOR]

The hydrogen storage material Lithium hydride (LiH) has received wide attention due to its high hydrogen density. However, the reaction process of LiH with H 2 O is complex, and the microscopic mechanism has not been reported. This paper reveals the microscopic mechanism by the ReaxFF reaction force field module of the Amsterdam Modeling Suite (AMS). Combined with Gaussian09 software, the rate constants and energy changes are determined in the reaction course. As a result, LiH reacts with H 2 O preferentially, forming Li--O bonds and shedding H from Li--H, which collides randomly to generate H 2 and H 2 LiO. As the reaction proceeds, there are by-products H 4 LiO 2 , HLiO, HLi 2 O, and H 2 Li 2 O generated. The reaction course of H 4 LiO 2 is a spontaneous exothermic reaction, and the strong chemical bonding force of Li to H prompts the formation of HLiO, HLi 2 O, and H 2 Li 2 O. 100% of H 2 comes from the H removed by LiH. Thus, LiH being fully involved in the reaction, the number of H 2 produced remains the same. • The microscopic mechanism of the products H 2 LiO, H 4 LiO 2 , HLiO, HLi 2 O, and H 2 Li 2 O were revealed. • The formation energy barrier of H 2 LiO is 0.78 kJ mol−1, accounting for 79% of the products. • The products H 4 LiO 2 , HLiO, H 2 Li 2 O, and HLi 2 O are further reactions of H 2 LiO with H 2 O and LiH, which have higher energy barriers. • 100% of the product H 2 comes from the H removed by LiH, while the H of H 2 O is difficult to cleave. • The number of H 2 production is constant after reaching the maximum as the temperature of the reaction simulation increases. [ABSTRACT FROM AUTHOR]

Previously unknown 2,4,6-triarylpyrimidines were synthesized by the condensation of benzamidine and 4-(methyl-, 4-butoxy)benzamidine hydrochlorides with (E)-1,3-diaryl-2-propen-1-ones in alcohol in the presence of KOH. The products were reacted with (E)-N-(2-chlorophenyl)-1-arylmethanimines in the KOH/LiH/DMF system to give 2,4-diaryl-6- and 2-aryl-4,6-bis{4-[(E)-2-arylvinyl]phenyl}pyrimidines. [ABSTRACT FROM AUTHOR]

• NFRHT between metaterminals made of SiC plate-supported LiH nanoparticles is studied. • Surface modes and hyperbolic modes can regulate near-field heat flux. • Underlying mechanisms for flux modulation are revealed via energy transmission coefficients. • Near-field heat flux is tunable at a fixed terminal gap. Near-field radiative heat transfer (NFRHT) can break through the blackbody limit by several orders of magnitude, bringing great thermal management opportunities. However, regulating the intensity NFRTH at a fixed terminal gap is still challenging. In this work, we theoretically investigate the NFRHT between two metaterminals separated by a vacuum gap using the dipolar model. Each metaterminal comprises a silicon carbide (SiC) substrate covered by periodic lithium hydride (LiH) nanoparticle arrays. We demonstrate that the surface and hyperbolic modes excited by the hybrid LiH/SiC metasurface can regulate the radiative heat flux between the two terminals. Effects of the radius of the LiH particle (r), the lattice constant of the particle arrays, and their ratio on NFRHT and the underlying regulation mechanisms are revealed. Results indicate that at a fixed vacuum gap of 100 nm, the total flux between the LiH/SiC metaterminals can be increased from weaker (0.69 × 104 W/m2) to stronger (2.79 × 104 W/m2) than that (1.33 × 104 W/m2) between SiC planar terminals when the particle radius increases from r = 25 to 75 nm. The physical mechanism of NFRHT modulation is revealed through the effective dielectric function and energy transmission coefficients in different scenarios. This work provides a controllable means for manipulating NFRHT between terminals at a fixed gap size. [ABSTRACT FROM AUTHOR]

• New type of non-symmetrical fluoroalkylated 1,3,5-triketones. • NMR studies of tautomeric equilibrium and ring-chain tautomerism of triketones. • The preparation of 2-(polyfluoroalkyl)−4 H -pyran-4-ones. In this work, we present a synthetic protocol for the synthesis of non-symmetrical fluoroalkylated triketones. The synthesis is based on the reaction of benzoyl acetones with esters in the presence of excess lithium hydride. The tautomeric equilibrium of triketones in CDCl 3 and DMSO‑ d 6 solutions was studied. The synthetic application of 1,3,5-triketones has been demonstrated. A method has been developed for the efficient synthesis of 2-aryl-6-(polyfluoroalkyl)-4 H -pyran-4-ones by dehydrative cyclization. [Display omitted] [ABSTRACT FROM AUTHOR]

The new polynucleating tripodal proligand H6tren(dpa)3, containing thirteen nitrogen donors of four different types, was designed, synthesized, and isolated in good yield (~60%) via a transition-metal-free triple N-arylation of H6tren with HXdpa (X = Br or F), using K2CO3 or Cs2CO3 as a base (H6tren = tris(2-aminoethyl)amine, HXdpa = 6-halogeno-N-(pyridin-2-yl)pyridin-2-amine). HFdpa was prepared with excellent yield (90-92%) by reaction of 2,6-difluoropyridine with 2-aminopyridine in LiH/toluene/pyridine and was found more reactive than HBrdpa, affording higher conversion and higher yield. Use of Cs2CO3 turned out to be essential for achieving high regioselectivity and eliminating overarylation almost completely. [ABSTRACT FROM AUTHOR]

The fundamental vibrational excitation energy and the dissociation energy of the main isotopologue of lithium hydride ( 7 LiH) are studied by the variational method using all-particle explicitly correlated Gaussian (ECG) basis sets. In this approach, electrons and nuclei are treated on equal footing, i.e. the Born–Oppenheimer approximation is not assumed. The leading relativistic ( ∼ α 2 ) and the dominating part of the quantum electrodynamics ( ∼ α 3 ) corrections to the energy levels are accounted for in the framework of the perturbation theory. The fundamental vibrational excitation energy and the dissociation energies obtained in the calculations are well within the error bars of the available experimental data. [ABSTRACT FROM AUTHOR]

The hydride oxides LiLnEuH2−xO2 (Ln=La, Ce, Pr, Nd and Sm) were synthesized by reaction of the lanthanide sesquioxides with europium monoxide, europium dihydride and lithium hydride under inert conditions at 750 °C as black powders. They crystallize in the tetragonal K2NiF4‐type structure (space group: I4/mmm) with a mixed Ln3+/Eu2+ occupation. The crystal structures of the europium representatives LiLaEuH2−xO2 and LiLaEuD2−xO2 were analyzed by powder neutron diffraction data at short wavelengths (λ=70 pm). Hydrogen (deuterium) and oxygen atoms occupy distinct crystallographic sites with considerable vacancy concentrations on the hydrogen positions (a=363.80(8) pm, c=1323.3(3) pm, c/a=3.637 for LiLaEuH1.26(4)O2 and a=363.43(5) pm, c=1321.6(2) pm, c/a=3.636 for LiLaEuD1.41(2)O2). Moving from the mixed Ln/Eu occupation in LiLnEuH2O2 to Ln=Eu2+, we obtained the mixed‐anionic phase LiEu2H3O, which crystallizes in the same structure type with a=370.04(2) pm, c=1317.32(8) pm and c/a=3.560. [ABSTRACT FROM AUTHOR]

The MgH2–LiH composites with different composition ratios were prepared by different ball milling times, and the hydrogen generation performances of the composites were investigated and compared. X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy techniques were adopted to elucidate the performance improvement mechanisms. The results show that the hydrogen generation yield and kinetics can be improved with the increase of LiH content significantly. For the 7MgH2–3LiH and 1MgH2–1LiH, with the increase of the ball milling time, the hydrogen yield increases firstly, and then decreases, but the kinetics almost do not change. This may be caused by the change of particle size of the composites after ball milling. However, for the 9MgH2–1LiH, the hydrogen yield increases with ball milling time but the kinetics decrease gradually. This may be due to the gradual movement of LiH from the surface to the interior of MgH2 and to the covering of MgH2 after ball milling. [ABSTRACT FROM AUTHOR]

Sputtering, reflection, and retention processes at amorphous and crystalline lithium hydride surfaces due to impact of low energy (1–100 eV) hydrogen and deuterium atoms over the range of 0o −85o angle of incidence at 300 K surface temperature were investigated by atomistic computational methods. Classical molecular dynamics simulations were performed with improved reactive bond-order force field (ReaxFF) potentials that include long-range polarization effects. In addition to probabilities of surface processes, the energy and angular spectra of ejected particles were obtained. Comparison of these results with those previously obtained on pristine lithium surfaces indicates the importance of saturation of the Li surface and near-surface region with hydrogen. We show that such saturation, which is typical in both laboratory and fusion device experiments with lithium coating of the plasma-facing surfaces, significantly changes the surface processes with hydrogen irradiation in the understudied low-energy region of impact energies.

Following the first principles, the elements of the analytic theory of potential curves for diatomic molecules (diatomics) are presented. It is based on matching the perturbation theory at small internuclear distances R and multipole expansion at large distances, modified by exponentially small terms for homonuclear case, with the addition of the phenomenologically described equilibrium configuration, if it exists. It leads to a new class of (generalised) rational potentials (modified by exponentially small terms) with a difference in degrees of polynomials in numerator and denominator equal to 4 (6) for positively charged (neutral) diatomics. For example, the He 2 + and LiH diatomics in Born–Oppenheimer approximation are considered. For 4 He 2 + ( 3 He 2 + ) diatomics it is found the approximate analytic expression for the potential energy curves (analytic PEC) V (R) for the ground state X 2 Σ u + and the first excited state A 2 Σ g + . It provides 3–4 s.d. correctly for distances R ∈ [ 1 , 10 ] a.u. with some irregularities for A 2 Σ g + PEC at small distances (much are smaller than equilibrium distances) probably related to level (quasi)-crossings that may occur there. The analytic PEC for the ground state X 2 Σ u + supports 829 (626) rovibrational states with 3–4 s.d. of accuracy in energy, which is only by 1 state less (more) than 830 (625) reported in the literature. The analytic PEC for the excited state A 2 Σ g + supports all 9 reported weakly-bound rovibrational states. For 7 LiH it is found the analytic expression for the ground state X 1 Σ + PEC in the form of a rational function, which supports 906 rovibrational states with 3–4 s.d. accuracy in energy, it is only of 5 states more than reported in the literature (901). For both diatomics, the difference in a number of rovibrational states is related to the non-existence/existence of weakly-bound states close to the threshold (to dissociation limit). Entire rovibrational spectra are found in a single calculation using the code based on the Lagrange mesh method. [ABSTRACT FROM AUTHOR]

In this work we present high-accuracy benchmark-quality calculations of the electron affinity (EA) of the LiH molecule in a framework that does not assume the Born–Oppenheimer (BO) approximation. The EA is calculated as a difference between the total energies of LiH − and LiH. The calculations of the energies are performed using the Rayleigh-Ritz variational method with large basis sets of all-particle explicitly correlated Gaussian functions (ECGs). Up to 14,000 ECGs are used in the calculations for each system. The nonlinear parameters of the ECGs are optimised by by the minimisation of the total non-relativistic energy of the system using an approach that employs the energy gradient determined with respect the parameters. The LiH − and LiH non-relativistic non-BO wave functions are subsequently used to calculate the leading relativistic corrections. The calculated EA is well converged in terms of the size of the basis sets and the obtained value falls within the uncertainty of the best available experimental result. [ABSTRACT FROM AUTHOR]

Two one-electron properties of the LiH molecule in its ground state at the internuclear distance of 3.015 bohr, namely the number of electrons and their kinetic energy, are decomposed into contributions due to projections (described by the quantum number m) of individual angular momenta onto the molecular axis. For sufficiently accurate electronic wavefunctions obtained with explicitly correlated Gaussian basis sets, the results of these partial-wave decompositions are found to obey the asymptotics valid at | m | → ∞ that stem from the off-diagonal cusp in the one-electron reduced density matrix. It turns out that the kinetic energy may be accurately extrapolated to the complete-basis-set limit, even if only the contributions pertaining to small values of | m | are available. [ABSTRACT FROM AUTHOR]

In this work we present high-accuracy benchmark-quality calculations of the electron affinity (EA) of the LiH molecule in a framework that does not assume the Born–Oppenheimer (BO) approximation. The EA is calculated as a difference between the total energies of LiH − and LiH. The calculations of the energies are performed using the Rayleigh-Ritz variational method with large basis sets of all-particle explicitly correlated Gaussian functions (ECGs). Up to 14,000 ECGs are used in the calculations for each system. The nonlinear parameters of the ECGs are optimised by by the minimisation of the total non-relativistic energy of the system using an approach that employs the energy gradient determined with respect the parameters. The LiH − and LiH non-relativistic non-BO wave functions are subsequently used to calculate the leading relativistic corrections. The calculated EA is well converged in terms of the size of the basis sets and the obtained value falls within the uncertainty of the best available experimental result. [ABSTRACT FROM AUTHOR]