Density Functional Theory Scheme Research Articles

Crossover from Linear to Quadratic Electro-optic Behavior in BaTiO_{3} and (Ba, Sr)TiO_{3} Solid Solution.

We derive a numerical method based on coupled density functional theory and effective Hamiltonian schemes to calculate the linear and quadratic electro-optic response of ferroelectrics at finite temperature and in different frequency ranges. By applying the developed method to BaTiO_{3}, we successfully resolve apparent discrepancies in the experimental literature that reported a linear or quadratic electro-optic response when visible or terahertz radiation was employed to measure the optical index, respectively. We further demonstrate that (and explain why), in the case of the Ba_{1-x}Sr_{x}TiO_{3} disordered solid solutions, structural phase transitions not only lead to larger linear electro-optic constants, as previously demonstrated in the literature, but also significantly enhance the quadratic electro-optic constants.

Toward Atomistic Understanding of Iron Phosphate Glass: A First-Principles-Based Density Functional Theory Modeling and Study of Its Physical Properties.

Iron phosphate glasses (IPGs) have been proposed as futuristic materials for nuclear waste immobilization and anode materials for lithium batteries. Recently, many attempts have been made to propose atomistic models of IPGs to explain their properties from an atomistic viewpoint. In this paper, we seek to produce small scale models of IPG that can be handled within the scheme of density functional theory (DFT) to study its electronic structure. The starting models, generated using the Monte Carlo (MC) method, were subsequently annealed using ab initio molecular dynamics (AIMD) to minimize the coordination defects. The geometry of the equilibrated structure was then optimized at 0 K. This hybrid approach (MC + AIMD + DFT optimization) produced good atomistic models of IPG, which can reproduce the experimentally observed band gap, vibrational density of states, magnetic moment of Fe, and mechanical and optical properties. Computationally expensive melt-quench simulation can be avoided using the present approach, allowing the use of DFT for accurate calculations of properties.

DFT calculations of the structural, elastic, and electronic properties of (Bi1−xFex)2Te3 chalcogenides

The crystal structure and elastic and electronic properties of (Bi1−xFex)2Te3 were studied by first-principles calculations within the Density Functional Theory (DFT) scheme. We found that at zero GPa, the lattice parameters for Bi2Te3 are in good agreement with the available experimental and theoretical data. As Fe replaces bismuth, the lattice parameter a increases while c decreases, changing the unit cell volume. According to Born’s structural stability criterion, the system is mechanically stable. Poisson’s ratio suggests a change from brittle to ductile behavior for (Bi1−xFex)2Te3 as iron increases. Also, Poisson’s ratio indicates that there is an ionic-covalent bond for x = 0.00 and behave as a metal as iron content increases. Vickers hardness decreases its value as Fe is introduced in the compound. Band structure calculations show that the results with spin orbit coupling (SOC) and without SOC are in good agreement with the experimental results. With SOC, a direct band gap at the Γ point is obtained with Eg = 0.138 eV concerning the 0.226 eV obtained without SOC. An evident modification of crystal structure in (Bi1−xFex)2Te3 shows a consistent trend, indicating a significant impact of iron incorporation on the structural properties. The electronic properties show a significant transformation with the introduction of iron, Bi2Te3 is characterized by a band gap, through iron doping the electronic structure shows a complete elimination of the band gap, marking a transition from semiconductor towards a conductor-like behavior. Density of states analysis provided insight into these changes, illustrating a modulation of electronic properties dependent on iron content.

Ultrafast hydrogen production in boron/oxygen-codoped graphitic carbon nitride revealed by nonadiabatic dynamics simulations.

Graphitic carbon nitride (g-C3N4 or GCN) shows promise in photocatalytic water splitting, despite facing the challenge of rapid electron-hole recombination. In this study, we investigated the influence of boron/oxygen codoping on the photocatalytic performance of GCN systems for hydrogen generation. First-principles calculations and nonadiabatic molecular dynamics (NAMD) simulations were employed to reveal that the recombination time of photogenerated carriers could be increased by 16% to 64% in the codoped systems compared to the pristine GCN. The time-dependent density functional theory (TDDFT) scheme was utilized to select energy windows and initiate dynamics in cluster models of B/O co-doped heptazine with water molecules. Notably, we observed efficient direct photodissociation of hydrogen atoms from water molecules within 60 fs and proton hops within the hydrogen-bonded network within 80 fs in the co-doped system, diverging from the previously proposed mechanism for pristine heptazine in NAMD simulations. This discovery underscores the significant role of faster proton-coupled electron transfer (PCET) reactions and rapid radiationless relaxation in achieving high photocatalytic efficiency in water splitting. Our work enhances the understanding of the internal mechanism of highly efficient photocatalysts for water splitting and provides a new design strategy for doped GCN.

Artificial Neural Network-Based Density Functional Approach for Adiabatic Energy Differences in Transition Metal Complexes.

During the past decades, approximate Kohn-Sham density functional theory schemes have garnered many successes in computational chemistry and physics, yet the performance in the prediction of spin state energetics is often unsatisfactory. By means of a machine learning approach, an enhanced exchange and correlation functional is developed to describe adiabatic energy differences in transition metal complexes. The functional is based on the computationally efficient revision of the regularized, strongly constrained, and appropriately normed functional and improved by an artificial neural network correction trained over a small data set of electronic densities, atomization energies, and/or spin state energetics. The training process, performed using a bioinspired nongradient-based approach adapted for this work from the particle swarm optimization, is analyzed and discussed extensively. The resulting machine learned meta-generalized gradient approximation functional is shown to outperform most known density functionals in the prediction of adiabatic energy differences for a diverse set of transition metal complexes with varying local coordinations and metal choices.

Effect of pressure in tuning the physical properties of MAX phase Zr2AN (A = In, Ga): A DFT scheme

The coexistence of metals and ceramics properties has made the MAX phase materials different from other three-dimensional materials. This study investigates several physical properties such as the structural, mechanical, and optoelectronic features of the pressure-induced Zr2AN (A = In, Ga) MAX phase via the density functional theory (DFT) insight. The lattice parameter c is greater than a (=b) as it is layered along the z direction. The electronic ground state energy and the applied pressure are inversely related. The elastic stiffness constants of the hexagonal crystal system have a positive and linear correlation with increasing pressure. The band structure reveals that both structures are electrically conductive at 0–50 GPa pressure range. The PDOS reveals the contribution of the Zr-4d orbital at the Fermi level. The optical parameters in the visible range point to possible optoelectronics and various technological applications.

Probing the structural, mechanical, phonon, thermal, and transport properties of magnetic halide perovskites XTiBr3 (X = Rb, Cs) through ab-initio results

Herein, we have first reported the intrinsic properties, including structural, mechanical, electronic, magnetic, thermal, and transport properties of XTiBr3 (X = Rb, Cs) halide perovskites within the simulation scheme of density functional theory as integrated into Wien2k. First and foremost, the structural stability in terms of their ground state energies has been keenly evaluated from their corresponding structural optimizations, which advocate that XTiBr3 (X = Rb, Cs) has a stable ferromagnetic rather than the competing non-magnetic phase. Later on, the electronic properties have been computed within the mix of two applied potential schemes like Generalized Gradient Approximation (GGA) along with Trans-Bhala modified Becke Johnson (TB-mBJ), which thoroughly addresses the half-metallic behaviour with spin-up as metallic and in contrast to opposite spin-down channel signatures the semiconducting behaviour. Furthermore, the spin-splitting seen from their corresponding spin-polarised band structures offers a net magnetism of 2 µB which lends their opportunities to unlock the application branch of spintronics. In addition, these alloys have been characterised to show their mechanical stability describing the ductile feature. Moreover, phonon dispersions decisively certify the dynamical stability within the density functional perturbation theory (DFPT) context. Finally, the transport and thermal properties predicted within their specified packages have also been forwarded in this report.

Ni2ZnAl BİLEŞİĞİNİN İLK PRENSİPLER YÖNTEMİ İLE İNCELENMESİ

In this study, ground state properties of Ni2ZnAl alloy in L21 phase from Heusler family were optimized. The calculated parameters are in harmony with the available literature data. Elastic constants were calculated using optimized parameters. The calculated elastic constants were found to meet the Born mechanical stability criteria. By using these constants, some mechanical and thermodynamic properties of the material such as elastic modulus, Vicker hardness, anisotropic nature, melting temperature were investigated in detail. Calculations showed that the Ni2ZnAl alloy is ductile, soft, and anisotropic. As such, it is a candidate material for applications that do not require hardness. The free energy, vibrational energy, entropy, and heat capacity of the Ni2ZnAl alloy were investigated using a semi- harmonic approach in the range of 0-800 K. All the total energy calculations were performed using the open-source Quantum Espresso software and ab-initio pseudopotential method based on the density functional theory (DFT) scheme within a generalized gradient approximation (GGA). According to the data obtained because of the study, Ni2ZnAl alloy is a potential candidate for industrial use.

Electronic properties of EuO and Eu2O3: FP-LAPW and LCAO computations and Compton spectroscopy strategies

Spin projected energy bands and density of states (DOS) have been deduced using full potential linearized augmented plane wave (FP-LAPW) with density functional theory (DFT) to analyze the electronic properties of EuO and Eu2O3. Whereas the Mulliken population (MP) and Compton profiles (CPs) for both the compounds have been computed using linear combination of atomic orbitals (LCAO) with pure and hybrid DFT (WC1LYP) schemes. The MP analysis indicates EuO to be more covalent than Eu2O3. Our first ever CP measurements for Eu2O3 (using 20 Ci 137Cs Compton spectrometer) indicate DFT with generalized gradient approximation and WC1LYP as successful prescriptions for predicting the electronic properties of such rare-Earth oxides. In addition, equally normalized experimental CPs of Eu2O3 are compared with other rare-Earth oxides RE2O3 (RE = Nd, Sm, Er and Yb) to decide an overall trend of localisation of f-electrons. A metallic behaviour of Eu2O3 is observed on the basis of real-space analysis of experimental, LCAO and free electron theory based CPs of Eu2O3.

Synergistically investigating the structural, magnetic, opto-electronic, and thermo-elastic traits of LaFe1−xNixO3 for novel electronic applications

Electronic materials have gained massive interest in the past few years. The fundamental reason is the growing industrial demands and efforts to discover novel low cost-effective materials. In this work, the influence of Ni substitution on LaFeO3 is presented in detail using the Kohn–Sham scheme of density functional theory. All studied compounds have shown good agreement with experimentally reported results. However, mechanical and optical results are reported for the first time for doped structures. The structural stability has been extensively checked through several stability criteria, such as, structural optimizations, elastic stability tests, and enthalpy of formation. Furthermore, the electronic and optical properties suggest highly conducting and reflecting phases of the studied compounds, respectively. The analysis of magnetic properties shows a decrease in magnetic moment value with an increase in Ni content due to Fe-Ni degeneracy. Mechanical analysis such as moduli of elasticity B, G, and Y has shown an increase in strength of 75% Ni substituted LaFeO3 by 24.5, 79.7, and 59.2%, respectively. Internal strain factor indicates majority bond flexibility, implying a potential application in flexible electronic devices.

First-Principles Study on Mechanical and Optical Behavior of Plutonium Oxide under Typical Structural Phases and Vacancy Defects.

The chemical corrosion aging of plutonium is a very important topic. It is easy to be corroded and produces oxidation products of various valence states because of its 5f electron orbit between local and non-local. On the one hand, the phase diagram of plutonium and oxygen is complex, so there is still not enough research on typical structural phases. On the other hand, most of the studies on plutonium oxide focus on PuO2 and Pu2O3 with stoichiometric ratio, while the understanding of non-stoichiometric ratio, especially for Pu2O3-x, is not deep enough. Based on this, using the DFT + U theoretical scheme of density functional theory, we have systematically studied the structural stability, lattice parameters, electronic structure, mechanical and optical properties of six typical high temperature phases of β-Pu2O3, α-Pu2O3,γ-Pu2O3, PuO, α-PuO2,γ-PuO2. Further, the mechanical properties and optical behavior of Pu2O3-x under different oxygen vacancy concentrations are analyzed and discussed in detail. The result shows that the elasticity modulus of single crystal in mechanical properties is directly related to the oxygen/plutonium ratio and crystal system. As the number of oxygen vacancies increases, the mechanical constants continue to increase. In terms of optical properties, PuO has the best optical properties, and the light absorption rate decreases with the increase of oxygen vacancy concentration.

First-principles calculations to investigate physical properties of single-cubic (Ba0.82K0.18)(Bi0.53Pb0.47)O3 novel perovskite superconductor

In the present study, the pseudopotential plane-wave (PP-PW) pathway in the scheme of density functional theory (DFT) is utilized to investigate the various unexplored physical properties of (Ba0.82K0.18)(Bi0.53Pb0.47)O3 (BKBPO) single perovskite superconductor. We have analyzed mechanical properties, elastic constants, and moduli at ambient temperature with zero and elevated pressures (up to 25 GPa) using the CASTEP code at equilibrium conditions as well. The calculated values of Poisson’s ratio, Pugh’s indicator, and Cauchy pressure show that the studied superconductor is ductile in nature at ambient conditions. The calculated machinability index and hardness values of BKBPO perovskite indicate its superior industrial applications compared to similar perovskites. The compound might be considered a promising thermal barrier coating (TBC) material based on Young’s modulus (E), and thermal shock coefficient (R) data. We also have investigated the anisotropic nature incorporating both the theoretical indices and graphical representations in 2D and 3D dimensions, which express a high level of anisotropy of the studied compound. The flatness of the energy bands near EF is a sign of Van-Hf singularity that might increase the electron pairing and origination of high-TC superconductivity. The computed band structure exhibits its metallic characteristics which is confirmed by the band overlapping in the diagram. A band of DOS is formed for the strong hybridization of the constituent elements where the O-2p orbital electrons contribute most dominantly at EF in contrast to all orbital electrons. The orbital electrons at the EF are seen maximum from both the partial density of states and charge density mapping. The coexistence of the electron and hole-like Fermi sheets exhibits the multi-band nature of the BKBPO superconductor. On the other hand, Fermi surfaces with flat faces promote transport features and Fermi surface nesting as well. The calculated value of the electron-phonon (e-ph) coupling constant (λ = 1.46) is slightly lower than that of isostructural superconductors, which indicates that the studied BKBPO can be treated as a strongly coupled superconductor identical to the previously reported isostructural perovskite superconductors. Furthermore, the thermodynamic properties have been evaluated and analyzed at elevated temperature and pressure by using harmonic Debye approximation (QHDA).

Going beyond the electric-dipole approximation in the calculation of absorption and (magnetic) circular dichroism spectra including scalar relativistic and spin-orbit coupling effects.

In this work, a time-dependent density functional theory (TD-DFT) scheme for computing optical spectroscopic properties in the framework of linearly and circularly polarized light is presented. The scheme is based on a previously formulated theory for predicting optical absorption and magnetic circular dichroism (MCD) spectra. The scheme operates in the framework of the full semi-classical field-matter interaction operator, thus generating a powerful and general computational scheme capable of computing the absorption, circular dichroism (CD), and MCD spectra. In addition, our implementation includes the treatment of relativistic effects in the framework of quasidegenerate perturbation theory, which accounts for scalar relativistic effects (in the self-consistent field step) and spin-orbit coupling (in the TD-DFT step), as well as external magnetic field perturbations. Hence, this formalism is also able to probe spin-forbidden transitions. The random orientations of molecules are taken into account by a semi-numerical approach involving a Lebedev numerical quadrature alongside analytical integration. It is demonstrated that the numerical quadrature requires as few as 14 points for satisfactory converged results, thus leading to a highly efficient scheme, while the calculation of the exact transition moments creates no computational bottlenecks. It is demonstrated that at zero magnetic field, the CD spectrum is recovered, while the sum of left and right circularly polarized light contributions provides the linear absorption spectrum. The virtues of this efficient and general protocol are demonstrated on a selected set of organic molecules where the various contributions to the spectral intensities have been analyzed in detail.

Catalytic reduction of carbon dioxide over two-dimensional boron monolayer

• This work studies the electrochemical reduction of CO 2 on boron nanosheets, metal-free catalyst, under the scheme of density functional theory (DFT) and microkinetic modeling. • The strain can turn metallic two-dimensional boron nanosheet to semiconductor, not only making boron sheets possess photo(electro)catalytic activity (1.4 eV), but also improving energy efficiency and selectivity performance against hydrogen evolution reaction. • Thermodynamic and microkinetic models are applied to demonstrate the favorable products, critical steps and hydrogenation mechanisms. • By introducing the aqueous electrolytes, the hydrated alkali cations not only effect on the CO 2 concentration, but also produce a bigger surface charge density and stronger interfacial electric filed. Carbon dioxide reduction (CRR) is an attractive strategy for alleviating global warming and producing valuable fuels. In this work, we study the catalytic conversion of CO 2 to C 1 -C 3 products on boron nanosheet in the presence of compressive strain by using density functional theory. Thermodynamic and microkinetic models are applied to demonstrate the favorable products, critical steps, and hydrogenation mechanisms. As demonstrated, the strain can turn metallic two-dimensional boron nanosheet to semiconductor, not only making boron sheets possess photo(electro)catalytic activity, but also improving energy efficiency and selectivity performance against hydrogen evolution reaction. By introducing the aqueous electrolytes, the hydrated alkali cations not only effect on the CO 2 concentration, but also produce a bigger surface charge density and stronger interfacial electric filed. Especially, the selectivity of C 2+ products is enhanced with the increase of alkali cations size by decreasing the kinetic barrier for CO dimerization and stabilizing the intermediates. The results highlight the significance of metal-free catalysts for CRR by the photoelectrochemical method and provide novel avenues for the development of new solar-energy utilization catalysts.

Cyclic and tensile deformations of Gold–Silver core shell systems using newly parameterized MEAM potential

Gold–Silver (Au–Ag) core-shell nanostructures have significant applicability in stretchable and biocompatible electronics where endurance under high tensile and cyclic loading is a requirement. This work, for the first time, quantitatively investigates the role of dislocations and defect interaction governing the mechanical behavior of Au–Ag and Ag–Au Core-shell nanostructures under tensile and cyclic loading using molecular dynamics (MD) simulation. For accurate representation of the underlying physics, a novel modified embedded atomic model (MEAM) interatomic potential for pristine Au, Ag and their alloys is parameterized through two different density functional theory (DFT) schemes. Using the new potential for MD simulations, the cyclic loading properties of pristine and core-shell nanowires (NWs) in a strain range of −15%–15% for 10 cycles are conducted. The tensile behavior of pristine and core-shell NWs is also explored for temperatures between 300 K and 600 K. A comparative analysis between Core-shell structures and their pristine counterparts are carried out. Our results suggest that Ag–Au Core-shell NW exhibit superior stress-strain reversibility under cyclic loading among the structures examined. Ag–Au exhibit the highest dislocation formation and near-complete annihilation of defects consistently. Au–Ag also present improved cyclic loading properties than its pristine counterparts. For tensile loading, all four structures exhibited deterioration in strength with increasing temperature. Thermal softening is observed to be more prominent in Au–Ag core-shell NWs compared to Ag–Au. Our work lays out a foundation for exploration of mechanical properties of Au–Ag systems using the MEAM potential which will help design components for stretchable electronics and creates a pathway for further exploration of similar binary alloy systems.

Revealing the oxygen Reduction/Evolution reaction activity origin of Carbon-Nitride-Related Single-Atom catalysts: Quantum chemistry in artificial intelligence

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are two critical reactions for renewable energy applications, such as water electrolysers and fuel cells. During the last decade, single-atom catalysts (SACs) deposited on carbon nitrides have been a rising star as superior electrocatalysts for ORR and OER. However, either experiments or theoretical simulations cannot screen all the possible SACs at a high speed and low cost. Herein, with the aid of density functional theory (DFT), machine learning (ML) and cross validation scheme, the best performing ML models (root mean square error = 0.24 V/0.23 V for ORR/OER) are established and implemented to describe the underlying pattern of easily obtainable physical and chemical properties and the ORR/OER overpotentials of carbon-nitride-related SACs. The best SACs recommended by the ML models are further verified by DFT calculations to confirm the reliability and accuracy of models. Three promising oxygen electrocatalysts with higher activity than noble metals are identified including RhPc, Co-N-C, and Rh-C4N3. The electron number of d orbital of the metal active site is determined as the most effective descriptor by further model analysis. Finally, the universal mathematical expressions which can accurately predict the catalytic activity of carbon-nitride-related SACs without DFT calculations and ML process are obtained. The revolutionary DFT-ML hybrid scheme opens a new avenue of rational and low-cost design principles of desirable catalysts and even the exploration of recondite activity origin in an interdisciplinary view.

Density functionals with spin-density accuracy for open shells.

Electrons in zero external magnetic field can be studied with the Kohn-Sham (KS) scheme of either density functional theory (DFT) or spin-DFT (SDFT). The latter is normally used for open-shell systems because its approximations appear to model better the exchange and correlation (xc) functional, but also because, so far the application of DFT implied a closed-shell-like approximation. In the first part of this Communication, we show that correcting this error for open shells allows the approximate DFT xc functionals to become as accurate as those in SDFT. In the second part, we consider the behavior of SDFT for zero magnetic field. We show that the KS equations of SDFT emerge as the generalized KS equations of DFT in this limit, thus establishing a so far unknown link between the two theories.

Solvation Free Energies in Subsystem Density Functional Theory.

For many chemical processes the accurate description of solvent effects are vitally important. Here, we describe a hybrid ansatz for the explicit quantum mechanical description of solute-solvent and solvent-solvent interactions based on subsystem density functional theory and continuum solvation schemes. Since explicit solvent molecules may compromise the scalability of the model and transferability of the predicted solvent effect, we aim to retain both, for different solutes as well as for different solvents. The key for the transferability is the consistent subsystem decomposition of solute and solvent. The key for the scalability is the performance of subsystem DFT for increasing numbers of subsystems. We investigate molecular dynamics and stationary point sampling of solvent configurations and compare the resulting (Gibbs) free energies to experiment and theoretical methods. We can show that with our hybrid model reaction barriers and reaction energies are accurately reproduced compared to experimental data.

Insight into the exemplary structural, elastic, electronic and optical nature of GaBeCl3 and InBeCl3: a DFT study.

In the scheme of density functional theory (DFT), Structural, elastic, electronic, and optical properties calculations of GaBeCl3 and InBeCl3 are carried out using Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) installed in Wein2k software. Structurally the compounds of interest are found to be stable. Both compounds possess elastic stability, anisotropy, and ductility determined by the elastic studies. The electronic-band structure analysis shows the semiconductor nature of GaBeCl3 and InBeCl3 compounds with indirect band gaps of ∼3.08 eV for GaBeCl3 and ∼2.04 eV for InBeCl3 along with the symmetrical points from (X–Γ). The calculated total density of states (TDOS) and partial density of states (PDOS) of these compounds reveal that for the GaBeCl3 compound, the contribution of Ga (4p) and Cl (3p) orbital states in the valence, as well as the conduction band, is dominant. While for InBeCl3, the contribution of Cl (3p) states as well as In (5s) is large in the valence band and in that of Cl (3p-states) states in the conduction band. The type of chemical bonding is found to be ionic in both compounds. The optical properties i.e., the real (ε1(ω)) and imaginary (ε2(ω)) parts of dielectric function, refractive index n(ω), optical reflectivity R(ω), optical conductivity σ(ω), absorption coefficient α(ω), energy loss L(ω) and electron extinction coefficient k(ω) are also discussed in terms of optical spectra. It is reported that n(ω) and k(ω) exhibit the same characteristics as ε1(ω) and ε2(ω) respectively. Efficient application of these materials can be seen in semiconducting industries and many modern electronic devices.

Magnetic properties of 3d, 4d, and 5d transition-metal atomic monolayers in Fe/TM/Fe sandwiches: Systematic first-principles study

Previous studies have accurately determined the effect of transition metal point defects on the properties of bcc iron. The magnetic properties of transition metal monolayers on the iron surfaces have been studied equally intensively. In this work, we investigated the magnetic properties of the 3d, 4d, and 5d transition-metal (TM) atomic monolayers in Fe/TM/Fe sandwiches using the full-potential local-orbital (FPLO) scheme of density functional theory. We prepared models of Fe/TM/Fe structures using the supercell method. We selected the total thickness of our system so that the Fe atomic layers furthest from the TM layer exhibit bulk iron-bcc properties. Along the direction perpendicular to the TM layer, we observe oscillations of spin and charge density. For Pt and W we obtained the largest values of perpendicular magnetocrystalline anisotropy and for Lu and Ir the largest values of in-plane magnetocrystalline anisotropy. All TM layers, except Co and Ni, reduce the total spin magnetic moment in the generated models, which is in good agreement with the Slater-Pauling curve. Density of states calculations showed that for Ag, Pd, Ir, and Au monolayers, a distinct van Hove singularity associated with TM/Fe interface can be observed at the Fermi level.