Complex Band Research Articles

NanoNET: An extendable Python framework for semi-empirical tight-binding models

We present a novel open-source Python framework called NanoNET (Nanoscale Non-equilibrium Electron Transport) for modeling electronic structure and transport. Our method is based on the tight-binding method and non-equilibrium Green’s function theory. The core functionality of the framework is providing facilities for efficient construction of tight-binding Hamiltonian matrices from a list of atomic coordinates and a lookup table of the two-center integrals in dense, sparse, or block-tridiagonal forms. The framework implements a method based on kd-tree nearest-neighbor search and is applicable to isolated atomic clusters and periodic structures. A set of subroutines for detecting the block-tridiagonal structure of a Hamiltonian matrix and splitting it into series of diagonal and off-diagonal blocks is based on a new greedy algorithm with recursion. Additionally the developed software is equipped with a set of programs for computing complex band structure, self-energies of elastic scattering processes, and Green’s functions. Examples of usage and capabilities of the computational framework are illustrated by computing the band structure and transport properties of a silicon nanowire as well as the band structure of bulk bismuth. Program summaryProgram Title:NanoNETCPC Library link to program files:https://doi.org/10.17632/b9p7kyzdj9.1Developer’s repository link:https://github.com/freude/NanoNetLicensing provisions: MITProgramming language: PythonNature of problem: The framework NanoNET solves a problem which is, having a set of atomic coordinates and tight-binding parameters, to construct Hamiltonian matrices in one of several desired forms. In particular, some applications require those matrices to have a reduced bandwidth and/or to possess a block-tridiagonal structure.Solution method: The problem is solved using a combination of kd-tree-based fast nearest-neighbor search and atomic coordinate sorting. Furthermore, a new greedy recursive algorithm is proposed for detecting block-tridiagonal structure of a matrix in a non-optimal way. Additionally, we propose an algorithm of a polynomial time for optimizing block sizes.Additional features: Although the resulting matrices can be processed by many existing software packages, the framework also has built-in standard tools for diagonalizing Hamiltonian matrices and computing Green’s functions that make it an independent tool for solving electronic structure and transport problems.

Transcriptional Regulation of Vih by Oct4 and Sox9 in Scylla paramamosain.

Mud crab (Scylla paramamosain) is one of the most economically-important marine crabs in China. However, research on mechanisms of reproductive regulation is not sufficient. Vitellogenesis-inhibiting hormone (VIH) is a member of the crustacean hyperglycemia hormones (CHH) family, which plays an essential role in the regulation of gonadal development and maturation in crustaceans, and current studies on the regulation of Vih transcription in crabs are relatively rare. Our previous studies on the transcriptional regulation of mud crab Vih (SpVih) have proved that the binding site of Oct4/Sox9 transcription factor may be the key region for positively regulating the expression of SpVih. In this study, the electrophoretic mobility shift assay (EMSA) experiment confirmed that the nuclear protein extracted from the eyestalk could bind to the key region of SpVih promoter, and these specific bindings were dependent on the presence of Oct4/Sox9 binding sites. Two specific binding complex bands were detected in the supershift group of EMSA supershift experiments by Oct4 and Sox9 antibodies, further confirming the specific recognition of these two transcription factors on the key regulatory region of SpVih. In vitro, Oct4 and Sox9 gene overexpression vectors and SpVih core promoter fragment vector were constructed and co-transfected into HEK293T cells. As a result, SpVih activity increased with the concentration of transcription factors. In vivo, when Oct4 and Sox9 dsRNA were injected into the eyestalks of mud crab, respectively, the expression level of SpVih decreased significantly after interference with Oct4 or Sox9, and the expression level of SpVtg in the ovary and hepatopancreatic increased. Both in vitro and in vivo experiments showed that Oct4 and Sox9 had a positive regulatory effect on SpVih. The GST pull-down experiment was carried out by purified Oct4 and Sox9 proteins, and the results showed that there was an interaction between them. It was speculated that they regulated the expression of SpVih through the interaction.

Charge Transfer Complex of Neostigmine with 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone: Synthesis, Spectroscopic Characterization, Antimicrobial Activity, and Theoretical Study.

BackgroundElectron donor–acceptor interactions are important molecular reactions for the activity of pharmacological compounds. The aim of the study is to develop a charge transfer (CT) complex: synthesis, characterization, antimicrobial activity, and theoretical study.Method and ResultsA solid CT complex of neostigmine (NSG) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was synthesized and characterized by infrared spectra, NMR, and UV–visible spectroscopy. The results confirm the formation of a CT complex. The stability of the CT complex between NSG and DDQ in acetonitrile was determined in solution via spectrophotometric measurement, ie, by calculating the formation constant, molar extinction coefficient, and different spectroscopic parameters. The stoichiometry of the formed NSG–DDQ complex was determined using Job's method. The absorption band of the NSG–DDQ complex can be used for the quantification of NSG.ConclusionThe DFT geometry optimization of NSG, DDQ, and the CT complex and the UV comparative study of both theoretical and experimental structures are presented. The experimental results confirm the charge transfer structure. The bacterial study shows that the NSG–DDQ complex has good antibacterial activity against both Gram-positive and Gram-negative bacteria as well as antifungal activity against Candida albicans.

Study on structural, mechanical, electronic, vibrational, optical and thermo-dynamical behaviour of ZB Structured BeZ (Z=S, Se and Te) using ATK-DFT

The present research is a systematic computational study focused on structural, mechanical, electronic, vibrational, optical and thermo-dynamical properties of zinc-blende (B3) structured beryllium chalcogenides BeZ (Z=S, Se, Te) compounds using ATK-DFT method using PZ and PBEsol exchange and correlation potentials within the local density approximation (LDA) and the generalized gradient approximation (GGA) respectively and their comparison. The k-point and energy cut-off values were tested and provided convergence in self-consistent calculations. The structural parameters such as lattice constant, bulk modulus, second order elastic constants (C11, C12, C44) and material properties (B, G, Y and σ) for these crystals are computed and discussed. To explain the electronic properties, electronic energy band structure, complex band structures, phonon band structure, phonon density of state and electron density distribution are plotted. The effect of pressure on elastic constant, material properties and phase transitions are also studied, including phase transition from ZB structure to NiAs appearing at 53 GPa, 49 GPa and 33 GPa for BeS, BeSe, and BeTe respectively.

Vibrational predissociation in the bending levels of the à state of C3Ar.

Vibrational predissociation (VP) has been observed in 16 bands of the C3Ar van der Waals complex near the 0 v2 0 - 000 (v2 = 2-, 4-, 2+) and 0 2- 2 - 100 bands of the Ã1Π-X̃1Σ+ g system of C3. New higher resolution wavelength-resolved emission (WRE) spectra covering a wider spectral range have been recorded for many of these C3Ar bands, which show that most of the features observed in fluorescence must be reassigned as emission from the C3 fragment. Two types of VP processes have been recognized. The first type gives rise to vibrationally hot C3 fragments, mostly following |Δv| = 1, |ΔP| = 1 propensity rules, where P is the vibronic angular momentum of C3. The second type gives vibrationally cooled fragments. The VP processes can change abruptly from one type to the other with comparatively small differences in vibrational energy. Although the initial states are associated with both orbital components of the C3, Ã1Πu state, most of the VP fragments belong to the lower orbital component. A dipole-induced dipole model has been used to interpret the observed ΔP- propensities. Ab initio calculations of the binding energies of the ground and excited electronic states of C3Ar have been carried out; the calculated values are consistent with estimates of ≤144 cm-1 and 164 cm-1, respectively, given by the WRE spectra.

Vibration attenuation analysis of periodic underground barriers using complex band diagrams

Vibrations propagating underground may have harmful effects on adjacent buildings and human health. Recently, the notion of phononic crystals has been introduced and applied to isolate vibrations below the ground. In this paper, considering the viscoelastic material model, the complex band diagrams are suggested to analyse the transportation of vibrations in the composite foundation consist of soil and different underground structures. In the complex band diagram, the minimum imaginary part of the wave vectors is taken as the index to measure the ability of the pile group to weaken vibrations. Several types of underground barriers, including circular piles, continuous walls, and multi-layer piles, are analysed. The result shows that multi-layer piles can induce local resonance and achieve an attenuation zone at the low-frequency level. The attenuation effect of periodic barriers is then verified by transmission models. The results show that the complex band diagrams can quantitatively evaluate the isolation effect of periodic barriers, which is beyond the capability of classic band diagrams.

Insights into negative differential resistance in MoS2 Esaki diodes: A first-principles perspective

\ce{MoS_2} is a two dimensional material with a band gap depending on the number of layers and tunable by an external electric field. The experimentally observed intralayer band-to-band tunneling and interlayer band-to-band tunneling in this material present an opportunity for new electronic applications in tunnel field effect transistors. However, such a widely accepted concept has never been supported up by theoretical investigations based on first principles. In this work, using density functional theory, in conjunction with non-equilibrilibrium Green's function techniques and our electric field gating method, enabled by a large-scale computational approach, we study the relation between band alignment and transmission in planar and side-stack \ce{MoS_2} $p$-$i$-$n$ junction configurations. We demonstrate the presence of negative differential resistance for both in-plane and interlayer current, a staple characteristic of tunnel diode junctions, and analyze the physical origin of such an effect. Electrostatic potentials, the van der Waals barrier, and complex band analysis are also examined for a thorough understanding of Esaki Diodes.

SPECTRAL PROPERTIES OF ZINC AND COBALT MESO-TETRAPHENYLPORPHYRINS IN POLYMER FILMS

The results of studying the spectral properties of zinc and cobalt meso-tetraphenyl-porphyrins included as the modifiers in polymethylmethacrylate, polystyrene and polyvinylchloride films are presented in this article for the first time. It was established that an inert polymer matrix of polyvinylchloride, block polystyrene and polymethylmethacrylate does not affect the spectral properties of tetrapyrrole macroheterocycles, which are included in it. In this case, insignificant bathochromic shift of the absorption bands of the metal complexes in the modified films is recorded, which is probably due to the presence of intermolecular interaction of the metalloporphyrin with the polymer matrix. The method of polymer producing is important for modification of polystyrene or polymethyl methacrylate films. The ignificant changes are observed in the electronic spectra of metalloporphyrins due to the interaction between the modifier and the residual amount of the radical polymerization initiator (benzoyl peroxide) used in the preparation of polymers. Earlier studies showed that the interaction of benzoyl peroxide with zinc and cobalt meso-tetraphenylporphyrinates in solution leads to the formation of the corresponding metalloisoporphyrinates. In this work, the possibility of such structures formation in a polymer matrix is shown for the first time. In this case, in the electronic absorption spectra of the modified films, as in solutions, bands appear in the near IR region. The fluorescent properties of modified films have been studied. It was shown that in the absence of interaction between the components in the film, metalloporphyrins introduced into the polymer matrix retain their ability to fluorescence.

Anatomy-based diagnostic criteria for complex body wall anomalies (CBWA).

BackgroundPrecise diagnosis and classification of CBWA cases can be challenging. BSA are considered when there is a body wall anomaly, skeletal abnormalities, and the umbilical cord is anomalous, absent or rudimentary, and LBWC when there is a body wall and structural limb anomalies with or without craniofacial abnormalities.MethodsPubMed was searched for body stalk anomalies, limb body wall complex, body stalk anomalies and amniotic band syndrome, and limb body wall complex and amniotic band syndrome. Sixty nine articles were selected and reviewed. This article systematically classifies the variants of CBWA in 218 cases, the study is based on the embryological and anatomical criteria established by Martín‐Alguacil and Avedillo to study BSA in the pig.ResultsEight different BSA presentation were defined. One hundred and eighty nine cases were classified as BSA, from which five were Type I, nine Type II, 20 Type III, 57 Type IV, 11Type V, 24 Type VI, 11 Type VII, and 52 Type VIII. Twenty six cases presented cranial phenotype, 114 abdominal phenotype, 42 cranio/abdominal overlapping phenotype, and five without defined phenotype. In addition, 52 BSA cases presented some kind of spinal dysraphism (SPDYS) and were classified as BSA/SPDYS, most of these cases did not show structural limb anomalies, except for three cases and were classified as LBWC/SPDYS.ConclusionThis morphology‐based classification represents a useful tool for clinical diagnosis, it helps to quantify and to evaluate CBWA in a precise, objective manner.

Wave attenuation in elastic metamaterial thick plates: Analytical, numerical and experimental investigations

We investigate the complex band structure and forced response of flexural waves propagating in an elastic metamaterial thick plate. Mindlin-Reissner thick plate theory is considered. We study the influence of periodic arrays of spring-mass resonators attached to the surface of a homogeneous thick plate on the formation of Bragg-type and locally resonant band gaps. The plane wave expansion and extended plane wave expansion approaches are used to compute the complex band structure and wave shapes of the metamaterial thick plate with attached spring-mass resonators. An experimental analysis is conducted with a 3D-printed metamaterial plate with resonators. Modal shapes, forced response and band structure are computed by finite element and wave finite element methods. Analytical, numerical and experimental results present good agreement.

Medium-Dependent Crossover from the Red to Blue Shift of the Donor's Stretching Fundamental in the Binary Hydrogen-Bonded Complexes of CDCl3 with Ethers and Ketones.

Mid-infrared spectra for C-D···O hydrogen (H)-bonded binary complexes of CDCl3 with acetone (AC), cyclohexanone (CHN), diethyl ether (DEE), and tetrahydrofuran (THF) have been measured in the vapor phase at room temperature and in an argon matrix at 8 K. Remarkable matrix effect has been observed in each case with respect to the spectral shift of the donor group's stretching fundamental (ΔνC-D). In the case of complexes with AC and CHN, the sign of ΔνC-D changes from a few wavenumbers positive (blue shift) in the vapor phase to a few tens of wavenumbers negative (red shift) in the argon matrix. For the two ether complexes, although no apparent reversal in the sign of ΔνC-D occurs, but the magnitudes of the red shifts in the matrix are manifold larger, and the bands appear with large enhancement in transition intensity. The medium effect has been explained consistently in terms of the local hyperconjugative charge transfer interaction at the H-bonding sites of the complexes and its interplay with the H-bond distance that varies with the physical conditions of the medium. Under the matrix isolation condition, νC-D bands of CHN and THF complexes depict a large number of substructures, which has been interpreted in terms of matrix site effect as well as Fermi resonance enhancement of the fingerprint combination tones and trapping of more than one isomer of the complexes in the matrix sites.

Ultrafast photoinduced band splitting and carrier dynamics in chiral tellurium nanosheets

Trigonal tellurium (Te) is a chiral semiconductor that lacks both mirror and inversion symmetries, resulting in complex band structures with Weyl crossings and unique spin textures. Detailed time-resolved polarized reflectance spectroscopy is used to investigate its band structure and carrier dynamics. The polarized transient spectra reveal optical transitions between the uppermost spin-split H4 and H5 and the degenerate H6 valence bands (VB) and the lowest degenerate H6 conduction band (CB) as well as a higher energy transition at the L-point. Surprisingly, the degeneracy of the H6 CB (a proposed Weyl node) is lifted and the spin-split VB gap is reduced upon photoexcitation before relaxing to equilibrium as the carriers decay. Using ab initio density functional theory (DFT) calculations, we conclude that the dynamic band structure is caused by a photoinduced shear strain in the Te film that breaks the screw symmetry of the crystal. The band-edge anisotropy is also reflected in the hot carrier decay rate, which is a factor of two slower along the c-axis than perpendicular to it. The majority of photoexcited carriers near the band-edge are seen to recombine within 30 ps while higher lying transitions observed near 1.2 eV appear to have substantially longer lifetimes, potentially due to contributions of intervalley processes in the recombination rate. These new findings shed light on the strong correlation between photoinduced carriers and electronic structure in anisotropic crystals, which opens a potential pathway for designing novel Te-based devices that take advantage of the topological structures as well as strong spin-related properties.

Isotope Effects in the Spectra of Hydrogen-Bonded Complexes. Anharmonic Calculations of Isotopologues of the [F(HF)2]– Complex

The frequencies and intensities for IR absorption bands of symmetric and asymmetric hydrogen-bonded complexes [FL1FL2F]– (L1, L2 = K-meson Ka, proton H, deuteron D, and triton T) are calculated. The equilibrium configuration and the potential energy and dipole moment surfaces of [FL1FL2F]– isotopologues were calculated by the MP2/6-311++G(3df,3pd) method with the basis set superposition error taken into account. The calculations of spectral parameters with allowance for anharmonic interactions of all vibrations were carried out using the second-order vibrational perturbation theory. Variation of L1 and L2 masses over wide limits led to significant changes in the forms of normal vibrations and anharmonic interaction constants upon isotopic substitution. The trends in the changes of spectral parameters were determined both upon transition from one symmetric isotopologue to another and upon transition from symmetric to asymmetric isotopologues. The frequency of the D–F stretching band of [FHFDF]– was predicted in good agreement with experimental information, and the assignment of this band was improved.

Controlling the Quantum Spin Hall Edge States in Two-Dimensional Transition Metal Dichalcogenides.

Two-dimensional transition metal dichalcogenides (TMDs) of Mo and W in their 1T' crystalline phase host the quantum spin Hall (QSH) insulator phase. We address the electronic properties of the QSH edge states by means of first-principles calculations performed on realistic models of edge terminations of different stoichiometries. The QSH edge states show a tendency to have complex band dispersions and coexist with topologically trivial edge states. We nevertheless identify two stable edge terminations that allow isolation of a pair of helical edge states within the band gap of TMDs, with monolayer 1T'-WSe2 being the most promising material. We also characterize the finite-size effects in the electronic structure of 1T'-WSe2 nanoribbons. Our results provide guidance to the experimental studies and possible practical applications of QSH edge states in monolayer 1T'-TMDs.

Two heteronuclear ZnII/CdII-DyIII complexes based on open-chain ether schiff base ligand: Synthesis, structures, fluorescence and antioxidation activity

Two open-chain ether Schiff base d-f heteronuclear complexes with bis(5-bromine-3-methoxysalicylidene)-3-oxapentane-1,5-diamine (H2L) and isonicotinate (IN), with composition [Zn2DyL2(OAc)(IN)](NO3)·2(CH3OH)·(CH2Cl2) and {[CdDyL(IN)(OAc)(NO3)(CH3OH)]·3(CH2Cl2)}n, have been synthesized by interfacial diffusion methods and further performed structural characterization. The structure analysis revealed that Zn-Dy complex is heterotrinuclear complex and DyIII ion acts as a joint bridging of two ZnL coordination units, whereas Cd-Dy complex is infinite 1D zigzag coordination polymer formed by CdDyL secondary units through bridging of isonicotinate. Fluorescence properties of 1–2 in the solid state and DMF solution at room temperature were also studied. It has been found that the emission spectra of complexes 1–2 do not exhibit corresponding DyIII ion characteristic emission peaks and the emission bands of complexes 1–2 are different due to the introduction of different transition metal ions. Antioxidation properties of the ligand and 1–2 were also studied, showing that the order of antioxidant activity is complex 2 > complex 1 > H2L. Thus, the structures and properties when constructing d-f heteronuclear complexes could be adjusted by selecting different transition metal ions such as ZnII ions and CdII ions.

Bulky-substituted phthalodinitriles and cobalt and copper phthalocyanines based on them: synthesis, thermal analysis and spectroscopic properties

By the nucleophilic substitution of the nitro group in 4-nitrophthalononitrile for the residues of alkoxy-substituted phenols, the synthesis of alkoxyphenoxyphthalonitriles was carried out. By template condensation of the substituted phthalonitriles obtained with copper and cobalt acetates at 200 °C, the corresponding phthalocyaninates were obtained. The conditions for the isolation and purification of the complexes synthesized were selected. The stability of substituted phthalonitriles and phthalocyaninates synthesized based on them regarding to heating in an argon–oxygen medium was evaluated (1:1 ratio). It was found the compounds obtained are thermally stable, and the destruction of phthalocyanines begins at lower temperatures compared to the corresponding phthalonitriles. For the complexes synthesized, the spectroscopic properties in organic solvents and concentrated sulfuric acid were studied. The influence of the nature of the substituent, metal complexing agent and solvent on the nature of the spectroscopic curves and the position of the main absorption band of phthalocyanine complexes has been established. It is noted passing from polar aprotic solvents to nonpolar ones, a shift of the maximum of the Q absorption band for the studied macrocycles was observed. Electronic absorption spectra in sulfuric acid show a significant bathochromic shift of the absorption band. An increase in the length of the alkyl substituent practically was found not to affect the position of the absorption maximum. Passing from complexes with Co(II) to Cu(II), a bathochromic shift of the absorption maximum was observed.

Influence of processing and pH on amino acid profile, morphology, electrophoretic pattern, bioactive potential and functional characteristics of alfalfa protein isolates

Protein isolates were prepared from wet heat processed (APIp) and unprocessed alfalfa seeds (APIc) and characterized for composition and functionality at different pH. APIc and APIp exhibited high content of all the essential amino acids. Antinutrient content of APIp was lower in comparison to APIc and marked reduction in the trypsin inhibitor (85.97%) and lectin activity (100%) was observed. Processing did not cause much reduction of bioactive constituents and antioxidant activity of APIp. Alfalfa protein isolates exhibited complex polypeptide banding ranging from molecular weight of 11–75 kDa. APIp exhibited change in the conformation of protein discerned as alteration in interrelated nuances of ATR-FTIR spectra, XRD-pattern, morphology, charge on proteins and reduced solubility in comparison to APIc due to processing. APIp exhibited marked improvement in the functional properties in comparison to APIc discerned as improved hydration, surface active and gelation properties. Highest hydration and surface active properties were exhibited at pH 9.0, even though APIp at pH 7.0 showed fairly similar functional properties as APIc and APIp at pH 9.0. APIp exhibited reduced least gelation concentration in comparison to APIc at pH 7.0 and also engendered gelation at pH 4.0 and 9.0 contrary to APIc.

Photoluminescence of Polymethylmethacrylate/(Zn,Cu,Ag)S:Eu3+ Compositions

Luminescent (Zn,Cu,Ag)S:Eu3+ nanoparticles (quantum dots, QDs) are synthesized upon decomposition of thioacetamide metal complexes in methylmethacrylate during block polymerization upon heating. The QD formation is confirmed by a corresponding band in the optical absorption spectrum of polymer compositions. Photoluminescence of polymethylmethacrylate/(Zn,Cu,Ag)S:Eu3+ compositions manifests itself as a complex band, related to crystal structure defects formed during doping of ZnS with copper and silver ions, and a set of narrow luminescence bands of Eu3+ ions. The luminescence is excited due to the interband transition and electronic transitions from the valence band to ZnS defect levels and intrinsic energy absorption by Eu3+ ions. The bond between Eu3+ ions and ZnS particles is confirmed by the dependence of the ZnS broadband luminescence intensity on the Eu3+ ion concentration and the increase in the intensity of the narrowband luminescence of Eu3+ ions as a result of energy transfer from the doped ZnS crystal levels to the energy levels of Eu3+ ions.

Active tuning of flexural wave in periodic steel-concrete composite beam with shunted cement-based piezoelectric patches

In this paper, flexural wave in a steel-concrete composite beam with periodically surface-bonded cement-based piezoelectric patches (CPP) is studied. The composite beam is designed using the idea of the phononic crystals. The external capacitor shunt circuit is connected to the CPP for regulating the band gap of the composite beam. The flexural wave equations are established by Euler beam theory. Using plane wave expansion method and transfer matrix method, the complex band structures of the flexural wave are calculated to investigate the frequency range and the vibration reduction in band gap. From the numerical results, it is shown that by tuning the external capacitor shunt circuit, the band gap of the periodic structure can be regulated conveniently. The regulation capability of the negative capacitance shunt circuit is stronger than that of the positive capacitance. We can obtain different starting low-frequency and wide band gaps by using negative capacitance. The proposed approach gives a promising way to design intelligent beams whose band gaps can be tuned without modifying the structures.

Role of quantum confinement and interlayer coupling in CrI3 -graphene magnetic tunnel junctions

Recent demonstrations of magnetic ordering and spin transport in two-dimensional heterostructures have opened research venues in these material systems. In order to control and enhance the tunneling magnetoresistance phenomena in 2D magnetic heterostructures beyond phenomenological descriptions, quantitative estimates of tunneling rates in terms of the atomic details are required. Here we combine first principles and quantum ballistic transport calculations to shed important insights from an atomistic viewpoint on the underlying mechanisms governing spin transport in graphene/${\mathrm{CrI}}_{3}$ junctions. Descriptions of the electronic structure reveal that tunneling is the dominant transport mechanism in these heterostructures and helps differentiate intermediate metamagnetic states present in the switching process. We find that quantum confinement and layer-layer interactions are key to describing transport in these two-dimensional systems. Ballistic transport calculations further support these findings and yield magnetoresistance values in remarkable agreement with experiments. The short width of these barriers limits analysis solely based on the bulk complex band structure often employed in the description of magnetic tunnel junctions. Our work devises mechanisms to attain larger tunneling magnetoresistances, proving valuable to the advancement of spin valves in layered heterostructures.