LiF Molecules Research Articles

Bracelet-like Complexes of Lithium Fluoride with Aromatic Tetraamides, and Their Potential for LiF-Mediated Self-Assembly: A DFT Study.

Geometries and binding energies of complexes between a LiF molecule and a model aromatic tetraamide are obtained using various DFT methods. The tetraamide consists of a benzene ring and four amides positioned so that the LiF molecule can bind via Li⋯O=C or N-H⋯F interactions. The complex with both interactions is the most stable one, followed by the complex with only N-H⋯F interactions. Doubling the size of the former resulted in a complex with a LiF dimer sandwiched between the model tetraamides. In turn, doubling the size of the latter resulted in a more stable tetramer with bracelet-like geometry having the two LiF molecules also sandwiched but far apart from each other. Additionally, all methods show that the energy barrier to transition to the more stable tetramer is small. The self-assembly of the bracelet-like complex mediated by the interactions of adjacent LiF molecules is demonstrated by all computational methods employed.

Interpretation of Coupled-Cluster Many-Electron Dynamics in Terms of Stationary States.

We demonstrate theoretically and numerically that laser-driven many-electron dynamics, as described by bivariational time-dependent coupled-cluster (CC) theory, may be analyzed in terms of stationary-state populations. Projectors heuristically defined from linear response theory and equation-of-motion CC theory are proposed for the calculation of stationary-state populations during interaction with laser pulses or other external forces, and conservation laws of the populations are discussed. Numerical tests of the proposed projectors, involving both linear and nonlinear optical processes for He and Be atoms and for LiH, CH+, and LiF molecules show that the laser-driven evolution of the stationary-state populations at the coupled-cluster singles-and-doubles (CCSD) level is very close to that obtained by full configuration interaction (FCI) theory, provided that all stationary states actively participating in the dynamics are sufficiently well approximated. When double-excited states are important for the dynamics, the quality of the CCSD results deteriorates. Observing that populations computed from the linear response projector may show spurious small-amplitude, high-frequency oscillations, the equation-of-motion projector emerges as the most promising approach to stationary-state populations.

How noninvasive treatment of uterine fibroids affects endometrial receptivity: a prospective cohort study

Objective To investigate the effect of the ultrasonic energy during MRI-guided high-intensity focused ultrasound ablation (HIFU) of uterine fibroids on molecular and tissue markers of endometrial receptivity in women of reproductive age. Material and methods A prospective cohort study of 60 women of reproductive age was conducted. The main group consisted of 32 patients suffering from the symptomatic course of uterine fibroids who received treatment with HIFU ablation of uterine fibroids. The control group consisted of 28 healthy fertile women examined voluntarily. The endometrium obtained with pipelle biopsy on days 20–22 of the cycle was examined by scanning electron microscopy and immunohistochemistry before and three months after the treatment. The results were processed by the method of variation statistics using the SPSS 22.0. Results The focused ultrasound rays passing through the endometrium did not cause any change in the maturation rate or the state of intercellular contacts. At the same time, a significant increase in the frequency of asynchronous maturation of pinopodia was found to be 14.28% before HIFU versus 50.00% after HIFU; p = .021 and the number of heteromorphic secretory cells 5.88% before HIFU versus 53.33% after HIFU; p = .002 in implantation endometrium. A significant decrease in the stromal expression of CD95+bright in the endometrium to the level comparable with control values was observed after HIFU (from 70.22 ± 9.77 c/s to 48.81 ± 5.47 c/s; p < .001; the control level − 47.80 ± 2.13 c/s). The ratio and expression of steroid receptors, proliferation markers, p53-dependent apoptosis and its blockers, regulators and markers of angiogenesis, LIF and LIF-R signaling molecules in the stroma and endometrial glands did not change significantly after treatment. Conclusion This study did not reveal any significant negative effects of HIFU ablation of uterine fibroids on endometrial receptivity in women of reproductive age.

First-principles study of the adsorption behaviors of Li atoms and LiF on the CF x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface.

Based on first principles calculation, the adsorption properties of Li atoms and LiF molecules on the fluorographene (CFx) surface with different F/C ratios (x = 1.0, 0.9, 0.8, 0.5 and ∼0.0) have been studied in the present work. The calculated binding energy of Li and CFx is greater than 2.29 eV under different F/C ratios, indicating that the battery has the potential to maintain a high discharge platform during the whole discharge process. But the adsorption energies of LiF on a CFx layer for different F/C ratios are 0.12–1.04 eV, which means LiF is not easy to desorb from a CFx surface even at room temperature. It will stay on the surface for a long time and affect the subsequent discharge. Current calculations also show the structure of the CFx-skeleton will change greatly during the reaction, when there are many unsaturated carbon atoms on the CFx surface, such as at x = 0.8 and 0.5. Moreover, the discharge voltage is strongly dependent on the discharge site. After discharge, the CFx-skeleton may continue to relax and release a lot of heat energy.

Photolysis of diatomic molecules as a source of atoms in planetary exospheres

We calculated the cross sections of photolysis of OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF molecules using quantum chemistry methods. The maximal values for photolysis cross sections of alkali metal monoxides are on the order of 10−18 cm2. The lifetimes of photolysis for quiet Sun at 1 astronomical unit are estimated as 2.0 × 105, 28, 5, 14, 2.1 × 105, 225, 42, 52, 2 × 106, 35 400, 486, and 30 400 s for OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF, respectively. We performed a comparison between values of photolysis lifetimes obtained in this work and in previous studies. Based on such a comparison, our estimations of photolysis lifetimes of OH, HCl, and HF have an accuracy of about a factor of 2. We determined typical kinetic energies of main peaks of photolysis-generated metal atoms. Impact-produced LiO, NaO, KO, NaCl, and KCl molecules are destroyed in the lunar and Hermean exospheres almost completely during the first ballistic flight, while other considered molecules are more stable against destruction by photolysis.

Practical approximation of the non-adiabatic coupling terms for same-symmetry interstate crossings by using adiabatic potential energies only.

A very simple equation, FijApp=[(∂2(Via-Vja)/∂Q2)/(Via-Vja)]1/2/2, giving a reliable magnitude of non-adiabatic coupling terms (NACTs, Fij's) based on adiabatic potential energies only (Via and Vja) was discovered, and its reliability was tested for several prototypes of same-symmetry interstate crossings in LiF, C2, NH3Cl, and C6H5SH molecules. Our theoretical derivation starts from the analysis of the relationship between the Lorentzian dependence of NACTs along a diabatization coordinate and the well-established linear vibronic coupling scheme. This analysis results in a very simple equation, α=2κ/Δc, enabling the evaluation of the Lorentz function α parameter in terms of the coupling constant κ and the energy gap Δc (Δc=|Via-Vja|Qc ) between adiabatic states at the crossing point QC. Subsequently, it was shown that QC corresponds to the point where FijApp exhibit maximum values if we set the coupling parameter as κ=[(Via-Vja)⋅(∂2(Via-Vja)/∂Q2)]Qc1/2/2. Finally, we conjectured that this relation could give reasonable values of NACTs not only at the crossing point but also at other geometries near QC. In this final approximation, the pre-defined crossing point QC is not required. The results of our test demonstrate that the approximation works much better than initially expected. The present new method does not depend on the selection of an ab initio method for adiabatic electronic states but is currently limited to local non-adiabatic regions where only two electronic states are dominantly involved within a nuclear degree of freedom.

Integrin αVβ3 and αVβ5 are required for leukemia inhibitory factor-mediated the adhesion of trophoblast cells to the endometrial cells

The embryo implantation including adhesion between trophoblast and endometrium is a crucial process for the successful pregnancy. LIF and adhesion molecules including integrins are known as significant factors for embryo implantation. However, the function of LIF on the regulation of adhesion molecule expression and promotion of trophoblast adhesion to endometrial cells has not been fully elucidated. Here we show that LIF significantly induced mRNA expression of ITGAV, ITGB3, and ITGB5 in endometrial cells, as evidenced by RT-PCR and qRT-PCR analysis. Based on the results from treatment of antagonist for LIF receptor (hLA), LIF positively regulates expression of integrin αV, β3, and β5, and adhesion of the human trophectoderm-derived JAr cells to endometrial Ishikawa cells. Furthermore, the adhesion between trophoblastic cells and LIF-stimulated endometrial cells was significantly reduced by neutralization of LIF-mediated integrin β3 and β5 expression on endometrial cell surface with integrin subunit β3 and β5 antibodies. Taken together, we firstly demonstrate that LIF enhances the adhesion of trophoblastic cells to endometrial cells by up-regulating expression of integrin heterodimer αVβ3 and αVβ5, indicating the promotion of endometrial receptivity for embryo implantation.

High-symmetry compact structures are preferred equilibrium configurations of LinFn + 1− (n = 2–5) superhalogen anions

Theoretical ab initio investigation performed for the LinFn+1− anionic systems (n=2–5) revealed that their most stable isomers correspond to the high-symmetry compact molecular structures exhibiting relatively large excess electron binding energies (exceeding 10eV). The formation of these polynuclear superhalogen anions was found to proceed spontaneously by a consecutive barrier-less attachment of neutral LiF molecules. Such a negative anionic cluster structural growth was predicted to be driven mainly by a successive increase of its electronic stability (manifested by an enlargement of the vertical electron detachment energy).

Distinct Solid‐Electrolyte‐Interphases on Sn (100) and (001) Electrodes Studied by Soft X‐Ray Spectroscopy

Soft X‐ray absorption spectroscopy with different probe depth was employed to characterize the solid electrolyte interphases (SEIs) formed on β‐Sn single crystals with two different surface orientations. Based on comparative studies of C‐K, O‐K, and F‐K absorption spectra between the SEIs and reference samples, SEI on Sn (100) mainly consists of porous Li2CO3 species with electrolyte uptake, while SEI on Sn (001) essentially consists of LiF and organic molecules, with a small amount of –CO3 and electrolyte buried inside. Theoretical calculation suggests that Sn (001) surface is more reactive than (100), especially after air exposure. The reactive (001) surface facilitates the decomposition of LiPF6 to form a LiF layer. In contrast, SEI on (100) surface is predominately from the typical decomposition of carbonate‐based electrolyte. While the LiF passivates Sn (001) electrode after one cycle, the porous carbonate layer on (100) surface does not prevent further decomposition of electrolyte after many cycles. This leads to drastically different electrochemical behavior and morphology of the two SEIs. The result is a direct proof that surface properties of active materials could strongly impact the SEI formation on electrodes even with the same electrolyte. Such effect could lead to distinct SEI formation and electrochemical performance.

Sputtering from swift-ion trails in LiF: A hybrid PIC/MD simulation

We model the sputtering of a LiF crystal induced by swift-ion impact. The impinging ion creates a trail of doubly ionized F+ ions, while simultaneously the corresponding electrons are set free. Ions move according to molecular dynamics, while excited electrons are treated by a particle-in-cell scheme. We treat the recombination time of electrons as a free parameter in our model. We find that the energy distribution of sputtered ions consists of 2 groups: a low-energy group centered at <1eV, and a high-energy group at 7–8eV. Fast ions (mainly Li+) are emitted early; these charge the surface negatively. Later, larger cluster ions and also neutral LiF molecules are emitted. Emission occurs at low angles to the surface normal. A jet along the normal direction can be observed, which is due to the electric field building up at the track surface. With increasing recombination time, processes are colder; sputtering decreases and the non-thermal jet structure becomes stronger.

Gating of a Water Nanochannel Driven by Dipolar Molecules

On the basis of molecular dynamics simulations, we investigate water permeation across a single-walled carbon nanotube (SWCNT) under the influence of four symmetrical half-rings, each having six LiF dipolar molecules. The flux remains almost fixed as the separation, R, between the rings and SWCNT is larger than 1.562 nm, but decreases significantly as 0.944 nm < R < 1.562 nm, and reaches zero as R < 0.944 nm. This nanochannel shows an excellent on-off gate that is both effectively resistant to dipole noises and sensitive to available signals. The finite element method reveals that the electrostatic field generated by LiF molecules plays a unique role in achieving the gating of the water SWCNT. Each water molecule tends to stay at the most stable state by moving to the location with the highest field strength in order to maintain its lowest electric energy. These findings may have biological implications because membrane water nanochannels made up of proteins accompanied with co-ions and counterions (due to ionization) share a similar single-file water chain inside the SWCNT with dipoles. The Appendix shows a possible link between the model system and a membrane water nanochannel with co-ions and counterions. Furthermore, our observations may have significance for the design of SWCNT-based nanoscale devices with dipolar molecules.

Photoelectron angular distributions from polar molecules probed by intense femtosecond lasers

We present numerical calculations of molecular-frame photoelectron angular distributions in strong-field ionization of oriented polar HF and LiF molecules by linearly polarized laser pulses with durations of about 20 fs (seven cycles at 800 nm). The calculations are performed within the single-active-electron and frozen-nuclei approximations. Our analysis shows that for the HF and LiF molecules, anisotropies in the molecular potential and the probed orbital lead to enhanced ionization during laser half cycles with the field pointing antiparallel to the permanent dipole of the dipole term in a multipolar expansion of the anisotropic molecular potential. This is manifested as a strong asymmetry in the computed photoelectron angular distributions: The photoelectrons are preferentially detected opposite to the permanent dipole of the molecular potential. This phenomenon is very sensitive to the probed system (the probed orbital and the molecular potential) and the orientation angle between the molecular axis and the laser polarization.

Application of improved virtual orbital based multireference methods to N2, LiF, and C4H6 systems

The improved virtual orbital (IVO) complete active space configuration interaction (CASCI) based multiconfigurational quasidegenerate perturbation theory (MCQDPT) and its single-root version (termed as MRMPPT) are applied to assess the efficacy and the reliability of these two methods. Applications involve the ground and/or excited state potential energy curves (PECs) of N(2), LiF, and C(4)H(6) (butadiene) molecules, systems that are sufficiently complex to assess the applicability of these methods. The ionic-neutral curve crossing involving the lowest two (1)Sigma(+) states of LiF molecule is studied using the IVO-MCQDPT method, while its single-root version (IVO-MRMPPT) is employed to study the ground state PEC for isomerization of butadiene and to model the bond dissociation of N(2) molecule. Comparisons with the standard methods (full CI, coupled cluster with singles and doubles, etc.) demonstrate that the IVO-based MRMPPT and MCQDPT approaches provide smooth and reliable PECs for all the systems studied. The IVO-CASCI method is explored to enable geometry optimization for ground state of C(4)H(6) using numerical energy gradients. The ground spectroscopic constants of N(2) and LiF determined using the numerical gradient based IVO-CASCI method are in accord with experiment and with other correlated calculations. As an illustration, we may point out that the maximum deviation from the experiment in our estimated normal mode frequency of LiF is 34 cm(-1), whereas for the bond length, the maximum error is just 0.012 A.

Quantum theory of chemical reactions in the presence of electromagnetic fields

We present a theory for rigorous quantum scattering calculations of probabilities for chemical reactions of atoms with diatomic molecules in the presence of an external electric field. The approach is based on the fully uncoupled basis set representation of the total wave function in the space-fixed coordinate frame, the Fock-Delves hyperspherical coordinates, and the adiabatic partitioning of the total Hamiltonian of the reactive system. The adiabatic channel wave functions are expanded in basis sets of hyperangular functions corresponding to different reaction arrangements, and the interactions with external fields are included in each chemical arrangement separately. We apply the theory to examine the effects of electric fields on the chemical reactions of LiF molecules with H atoms and HF molecules with Li atoms at low temperatures and show that electric fields may enhance the probability of chemical reactions and modify reactive scattering resonances by coupling the rotational states of the reactants. Our preliminary results suggest that chemical reactions of polar molecules at temperatures below 1 K can be selectively manipulated with dc electric fields and microwave laser radiation.

Geometry optimization using improved virtual orbitals: A complete active space numerical gradient approach

The improved virtual orbital-complete active space configuration interaction (IVO-CASCI) method is extended to enable geometry optimization and the calculation of vibrational frequencies for ground and excited states using numerical energy gradients. Applications consider the ground state geometries and vibrational frequencies of the Be2, LiF, H2S, and HCN molecules, as well as excited state properties for HCN, systems that are sufficiently complex to access the efficacy of the method. Comparisons with other standard approaches (self-consistent field, second order Moller-Plesset perturbation theory, complete active space self-consistent field, and coupled cluster singles and doubles methods) demonstrate that the numerical gradient version of the IVO-CASCI approach generally fares comparable to or better for all systems studied. The accurate estimates for the Be2 bond length and vibrational frequency are notable since many other computationally facile methods produce poor results.

Enhanced thermal stability in organic light-emitting diodes through nanocomposite buffer layers at the anode/organic interface

The effect of doped buffer layers at the anode/organic interface in small molecule organic light-emitting diodes was investigated. Appropriate doping of N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) and Cu-phthalacyanine (CuPc) layers using LiF or C60 molecules leads to improved interfacial morphology and thermal stability for both standard indium tin oxide or metals anodes, such as Au and Ag. Graded interfaces remain stable at temperatures well above the hole transport layer (i.e., NPB) glass transition temperature.

Relaxation of STO-3G and 6-31G* basis set functions in the series of LiF isoelectronic molecules of second row elements

The relaxation effect of functions of STO-3G and 6-31G* basis sets (BS) on their balance is considered in the series of LiF, BeO, BN, and C2 isoelectronic molecules. The values of parameters (exponential factors of basis functions, orbital exponents of Gaussian primitives, and contraction coefficients for the basis functions in molecules are found by the energy minimum criterion from unrestricted Hartree-Fock (UHF) calculations with a direct optimization of parameters: the simplex and Rosenbrock methods. Several optimization schemes differing in the number of parameters varied are performed. An important, from the practical viewpoint, relation between parameters of the basis functions of the sets in question is found through the mean values of Gaussian exponents. The relaxation effect on the variation of the total energy and relative errors in the calculations of interatomic distances, normal vibration frequencies, dissociation energies, and other properties of molecules are examined. The variation of the total energy upon the relaxation of STO-3G and 6-31G* basis functions (RBF) can achieve 1100 kJ/mole and 80 kJ/mole, respectively, and should be taken into account when evaluating energy characteristics, especially for the systems with high polar chemical bonds. The relaxation of STO-3G BS improves the description of molecular properties almost in all cases considered, whereas the relaxation of 6-31G* BS slightly affects its balance.

Evolution of the (hyper)polarizability with the size and periodicity of the system. A model investigation from the LiF molecule to the LiF 3D crystal

A finite field (FF) perturbation method, implemented in the CRYSTAL program, is used to investigate the evolution of the response to an applied electric field of systems of increasing size and dimensionality. LiF molecules, chains, slabs and bulk have been considered as model systems. (LiF)$_M$ molecules of increasing length are compared with the periodic infinite linear chain data; systems containing an increasing number of parallel linear chains are compared with the single layer slab, and slabs of increasing thickness are compared with bulk results. The same hamiltonian (Hartree-Fock), Li-F distance and basis set have been used for all systems. Sharp variations are observed in the response properties along the series (from the molecule to the 3D crystal), that are not the same for the parallel and perpendicular components of the tensors. In particular the (hyper)polarizability tensor components can vary by as much as a factor 8.

Ionisation Potential, Electron Affinity and Polar Bond: A First-order Correction Method for Interaction Energy

A new first-order method is proposed to improve the potential energy of the polar molecules. The nature of the polar bonding is illustrated by some examples, LiF, LiO, LiH, ScO, and AlO molecules, covering from strong to weak ionic cases. A simple first-order correction method using the dipole moment or the effective charge, and the experimental and theoretical ionisation potentials and electron affinities is explained. Application of this method to those molecules improves remarkably the spectroscopic constants. This method can be easily extended to polyatomic cases involving a polar bonding between an electropositive moiety (electron donor) and an electronegative functional group (electron acceptor).

Ornstein-Uhlenbeck diffusion quantum Monte Carlo study on the bond lengths and harmonic frequencies of some first-row diatomic molecules.

This article accesses the performance of the Ornstein-Uhlenbeck diffusion quantum Monte Carlo with regard to the calculation of molecular geometries and harmonic frequencies of H2, LiH, HF, Li2, LiF, CO, N2, and F2 molecules. A comparison of the results for the eight first-row diatomic molecules from experiments, CCSD(T)/6-311G(3df,3pd) and CCSD(T)/cc-pV5Z levels of theory as well as our work is given. The results presented show that quantum Monte Carlo is becoming powerful tools for ab initio electronic structure calculations.