Calculation Of Polarizabilities Research Articles

Theoretical Investigation of Electric Polarizability in Porphyrin-Zinc and Porphyrin-Zinc-Thiazole Complexes Using Small Property-Oriented Basis Sets.

Porphyrin complexes are of great importance due to their possible applications as sensors, solar cells and photocatalysts, as well as their ability to bind additional ligands. A valuable source of knowledge on their nature is their electric properties, which can be evaluated employing density functional theory (DFT) methods, supporting the experimental research. The present work aims at the application of small property-oriented basis sets in calculation of electric properties in transition metals, their oxides and test coordination complexes. Firstly, the existing polarized ZPol basis set for the first-row transition metals is modified in order to improve atomic polarizability results. For this purpose, optimization of the f-type polarization function exponent is carried out with respect to the value of average atomic polarizability of investigated metals. Next, both the original and the modified basis sets are employed in finite field CCSD(T) calculation of transition metal oxides' dipole moments, as well as DFT calculation of polarizabilities in porphyrin-zinc and porphyrin-zinc-thiazole complexes. The obtained results show that the ZPol and ZPol-A basis sets can be successfully employed in the calculation of linear electric properties in large systems. The optimization procedure used in the present work can be employed for other source basis sets and elements, leading to new efficient polarized basis sets.

Nucleon Electric Polarizabilities and Nucleon-Pion Scattering at the Physical Pion Mass.

We present a lattice QCD calculation of the nucleon electric polarizabilities at the physical pion mass. Our findings reveal the substantial contributions of the Nπ states to these polarizabilities. Without considering these contributions, the lattice results fall significantly below the experimental values, consistent with previous lattice studies. This observation has motivated us to compute both the parity-negative Nπ scattering up to a nucleon momentum of ∼0.5 GeV in the center-of-mass frame and corresponding Nγ^{*}→Nπ matrix elements using lattice QCD. Our results confirm that incorporating dynamic Nπ contributions is crucial for a reliable determination of the polarizabilities from lattice QCD. This methodology lays the groundwork for future lattice QCD investigations into various other polarizabilities.

NMR Spectroscopy and Multiscale Modeling Shed Light on Ion-Solvent Interactions and Ion Pairing in Aqueous NaF Solutions.

The balance between ion solvation and ion pairing in aqueous solutions modulates chemical and physical processes from catalysis to protein folding. Yet, despite more than a century of investigation, experimental determination of the distribution of ion-solvation and ion-pairing states remains elusive, even for archetypal systems like aqueous alkali halides. Here, we combine nuclear magnetic resonance (NMR) spectroscopy and multiscale modeling to disentangle ion-solvent interactions from ion pairing in aqueous sodium fluoride solutions. We have developed a high-accuracy method to collect experimental NMR resonance frequencies for both ions as functions of temperature and concentration. Comparison of these data with resonance frequencies for nonassociating salts allows us to differentiate the influence of solvation and ion pairing on NMR spectra. These high-quality experimental NMR data are used to validate our modeling framework comprising polarizable force field molecular dynamics (MD) simulations and quantum chemical calculations of NMR resonance frequencies. Our experimental and theoretical resonance frequency shifts agree over a wide range of temperatures and concentrations. Structural analysis reveals how both trends are dominated by interactions with water molecules. For the more sensitive 19F nucleus, the NMR resonance frequency decreases as hydrogen bonds between fluoride and water molecules are reduced in number with increased temperature and molality. Through a detailed analysis of the theoretical NMR resonance frequencies for both ions, we show that NMR spectroscopy can distinguish both contact ion pairs and single-solvent-separated ion pairs from free ions. This quantitative framework can be applied directly to other systems.

A comparative study of transition oscillator strengths and static polarizabilities of the hydrogen atom confined in Gaussian potential

Abstract The multipole (dipole, quadrupole, and octopole) photon-absorption transition oscillator strengths for the ground state of hydrogen atom confined in Gaussian potential are investigated for a great variety of potential depths and confining radii. It is interestingly found that at fixed potential depth the gradual increase of confining radius shows first destructive and then constructive effect on the multipole oscillator strengths. Such an effect can be understood from the overlap between the initial and final states. Multipole polarizabilities of the system are obtained through the sum-over-states formalism where the contributions from both the bound and continuum spectra of the system are included. Although the separate bound and continuum contributions can not be determined accurately, due to the long-range nature of the Coulomb potential introduced by the nucleus, their summations can be obtained to reasonably good accuracy, leading to fast convergence of numerical calculations of multipole polarizabilities. The present results are compared with previous calculations available in the literature. Although good agreement is observed for the dipole polarizability, significant differences exist in the quadrupole polarizability and orders-of-magnitude differences appear in the octopole polarizability. The possible reason for such large differences is analyzed by comparing the sum rule of corresponding oscillator strengths.

Calculating Molecular Polarizabilities Using Exact Frozen Density Embedding with External Orthogonality.

Frozen density embedding (FDE) with freeze-thaw cycles is a formally exact embedding scheme. In practice, this method is limited to systems with small density overlaps when approximate nonadditive kinetic energy functionals are used. It has been shown that the use of approximate nonadditive kinetic energy functionals can be avoided when external orthogonality (EO) is enforced, and FDE can then generate exact results even for strongly overlapping subsystems. In this work, we present an implementation of exact FDEc-EO (coupled FDE TDDFT with EO) for the calculation of polarizabilities in the Amsterdam density functional program package. EO is enforced using the level-shift projection operator method, which ensures that orbitals between fragments are orthogonal. For pure functionals, we show that only the symmetric EO contributions to the induced density matrix are needed. This leads to a simplified implementation for the calculation of polarizability that can exactly reproduce the supermolecular TDDFT results. We further discuss the limitation of exact FDEc-EO in interpreting subsystem polarizabilities due to the nonunique partitioning of the total density. We show that this limitation is due to the fact that subsystem polarizability partitioning is dependent on how the subsystems are initially polarized. As supermolecular virtual orbitals are exactly reproduced, this dependence is attributed to the description of the occupied orbitals. In contrast, for excitations of subsystems that are localized within one subsystem, we show that the excitation energies are stable with respect to the order of polarization. This observation shows that impacts from the nonunique nature of exact FDE on subsystem properties can be minimized by better fragmentation of the supermolecular systems if the property is localized. For global properties like polarizability, this is not the case, and nonuniqueness remains independent of the fragmentation used.

Optical n(p, T90) Measurement Suite 3: Results at λ=1542nm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda = 1542\\,\ ext{nm}$$\\end{document}

Single-isotherm n(p, T90) results are reported for the gases Ar, N2, H2O, and D2O at vacuum wavelength λ=1542.383(1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda = 1542.383(1)$$\\end{document} nm. The argon and nitrogen isotherms were measured near 303 K; the water isotherms were measured near 373 K. Combined with the two previous articles of this series, the present results beget several insights via dispersion analyses. The argon result is highly consistent with static measurement plus ab initio calculation of dispersion polarizability. The nitrogen result is nominally consistent with one recent experiment and the dipole oscillator strength distributions, but the present work offers a refined estimate of the molar refractivity at optical wavelengths. For ordinary and heavy water, the dispersion trend is nominally consistent with existing liquid measurements. However, water’s absorption features in the near-infrared preclude a reliable comparison of the present result with literature.

Standard Response Calculation of Electric Dipole Polarizability and Specific Optical Rotation Power Densities.

A time-dependent method has been developed to solve the standard response equation for the calculation of dynamic molecular property densities, endowed with the characteristic of being origin-invariant, entirely in the atomic orbital basis at both HF and DFT level of theory. The method has been tuned in particular for the calculation of origin-independent electric dipole polarizability density and specific rotation power density. Some demonstrations are given for the hexabenzocoronene molecule and the Tröger's base.

Prospects of a thousand-ion Sn2+ Coulomb-crystal clock with sub-10−19 inaccuracy

Optical atomic clocks are the most accurate and precise measurement devices of any kind, enabling advances in international timekeeping, Earth science, fundamental physics, and more. However, there is a fundamental tradeoff between accuracy and precision, where higher precision is achieved by using more atoms, but this comes at the cost of larger interactions between the atoms that limit the accuracy. Here, we propose a many-ion optical atomic clock based on three-dimensional Coulomb crystals of order one thousand Sn2+ ions confined in a linear RF Paul trap with the potential to overcome this limitation. Sn2+ has a unique combination of features that is not available in previously considered ions: a 1S0 ↔ 3P0 clock transition between two states with zero electronic and nuclear angular momentum (I = J = F = 0) making it immune to nonscalar perturbations, a negative differential polarizability making it possible to operate the trap in a manner such that the two dominant shifts for three-dimensional ion crystals cancel each other, and a laser-accessible transition suitable for direct laser cooling and state readout. We present calculations of the differential polarizability, other relevant atomic properties, and the motion of ions in large Coulomb crystals, in order to estimate the achievable accuracy and precision of Sn2+ Coulomb-crystal clocks.

Electric dipole polarizability of low-lying excited states in atomic nuclei

New equations for the electric dipole polarizability α E1 of low-lying excited states in atomic nuclei—and the related (−2) moment of the total photo-absorption cross section, σ −2—are inferred in terms of electric dipole and quadrupole matrix elements. These equations are valid for arbitrary angular momenta of the initial/ground and final/excited states and have been exploited in fully converged 1ℏ ω shell-model (SM) calculations of selected p- and sd-shell nuclei that consider configuration mixing; advancing previous knowledge from 17O to 36Ar, where thousands of electric dipole matrix elements are computed from isovector excitations which include the giant dipole resonance (GDR) region. Our results are in reasonable agreement with previous SM calculations and follow—except for 6,7Li and 17,18O—Migdal’s global trend provided by the combination of the hydrodynamic model and second-order non-degenerate perturbation theory. Discrepancies in 6,7Li and 17O arise as a result of the presence of α-cluster configurations in odd-mass nuclei, whereas the disagreement in 18O comes from the mixing of intruder states, which is lacking in the SM interactions. More advanced ab initio calculations of the dipole polarizability for low-lying excited states covering all the isovector states within the GDR region are missing and could be very valuable to benchmark the results presented here and shed further light on how atomic nuclei polarize away from the ground state

Realization of the pascal based on argon using a Fabry-Perot refractometer.

Based on a recent experimental determination of the static polarizability and a first-principle calculation of the frequency-dependent dipole polarizability of argon, this work presents, by using a Fabry-Perot refractometer operated at 1550 nm, a realization of the SI unit of pressure, the pascal, for pressures up to 100 kPa, with an uncertainty of [(1.0 mPa)2 + (5.8 × 10-6P)2 + (26 × 10-12P2)2]1/2. The work also presents a value of the molar polarizability of N2 at 1550 nm and 302.9146 K of 4.396572(26) × 10-6 m3/mol, which agrees well with previously determined ones.

Conditions for the efficiency of optical limiting based on experiment and quantum chemical calculations.

The development of suitable protection against laser radiation has proven challenging due to the lack of predictive models. The purpose of this article is to exclude the existing drawback by creating a universal strategy based on correlations between experimental and theoretical data characterizing the nonlinear optical properties of absorbers, for which a series of low-symmetry penta(chloro)cyclotriphosphazene-substituted monophthalocyanines was chosen. To search for correlations on a small series of dyes, we used the advanced algorithm CORRELATO, which has been proven to construct even the most unusual relationships demonstrated in our previous works. Due to the reducing symmetry of molecules, large values of the nonlinear absorption coefficient (more than 3000 cm GW-1) and, as a result, wide dynamic ranges (up to 630) with a high degree of attenuation of nanosecond laser radiation (10-20 times) were achieved. The use of the finite-field DFT method has allowed the calculation of dipole moments, polarizabilities and hyperpolarizabilities. The numerical data obtained during the calculations were used in correlations of theory vs. experiment to derive mathematical expressions (inequalities) to assess the effectiveness of absorbers in limiting the power of laser radiation.

Extension of the D3 and D4 London dispersion corrections to the full actinides series.

Efficient dispersion corrections are an indispensable component of modern density functional theory, semi-empirical quantum mechanical, and even force field methods. In this work, we extend the well established D3 and D4 London dispersion corrections to the full actinides series, francium, and radium. To keep consistency with the existing versions, the original parameterization strategy of the D4 model was only slightly modified. This includes improved reference Hirshfeld atomic partial charges at the ωB97M-V/ma-def-TZVP level to fit the required electronegativity equilibration charge (EEQ) model. In this context, we developed a new actinide data set called AcQM, which covers the most common molecular actinide compound space. Furthermore, the efficient calculation of dynamic polarizabilities that are needed to construct CAB6 dispersion coefficients was implemented into the ORCA program package. The extended models are assessed for the computation of dissociation curves of actinide atoms and ions, geometry optimizations of crystal structure cutouts, gas-phase structures of small uranium compounds, and an example extracted from a small actinide complex protein assembly. We found that the novel parameterizations perform on par with the computationally more demanding density-dependent VV10 dispersion correction. With the presented extension, the excellent cost-accuracy ratio of the D3 and D4 models can now be utilized in various fields of computational actinide chemistry and, e.g., in efficient composite DFT methods such as r2SCAN-3c. They are implemented in our freely available standalone codes (dftd4, s-dftd3) and the D4 version will be also available in the upcoming ORCA 6.0 program package.

Demonstration of a Transportable Fabry-Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes.

Fabry-Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10-90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry.

Colossal C130 Fullertubes: Soluble [5,5] C130-D5h(1) Pristine Molecules with 70 Nanotube Carbons and Two 30-Atom Hemifullerene End-caps.

We report the seminal experimental isolation and DFT characterization of pristine [5,5] C130-D5h(1) fullertubes. This achievement represents the largest soluble carbon molecule obtained in its pristine form. The [5,5] C130 species is the highest aspect ratio fullertube purified to date and now surpasses the recent gigantic [5,5] C120-D5d(1). In contrast to C90, C100, and C120 fullertubes, the longer C130-D5h has more nanotubular carbons (70) than end-cap fullerenyl atoms (60). Starting from 39,393 possible C130 isolated pentagon rule (IPR) structures and after analyzing polarizability, retention time, and UV-vis spectra, these three layers of data remarkably predict a single candidate isomer and fullertube, [5,5] C130-D5h(1). This structural assignment is augmented by atomic resolution STEM data showing distinctive and tubular "pill-like" structures with diameters and aspect ratios consistent with [5,5] C130-D5h(1) fullertubes. The high selectivity of the aminopropanol reaction with spheroidal fullerenes permits facile separation and removal of fullertubes from soot extracts. Experimental analyses (HPLC retention time, UV-vis, and STEM) were synergistically used (with polarizability and DFT property calculations) to down select and confirm the C130 fullertube structure. Achieving the isolation of a new [5,5] C130-D5h fullertube opens the door to application development and fundamental studies of electron confinement, fluorescence, and metallic character for a fullertube series of molecules with systematic tubular elongation. This [5,5] fullertube family also invites comparative studies with single-walled carbon nanotubes (SWCNTs), nanohorns (SWCNHs), and fullerenes.

Atomistic polarization model for Raman scattering simulations of large metal tips with atomic-scale protrusions at the tip apex

Abstract Tip-enhanced Raman spectroscopy (TERS) has recently been developed to push the spatial resolution down to single-chemical-bond scale. The morphology of the scanning tip, especially the atomistic protrusion at the tip apex, plays an essential role in obtaining both high spatial resolution and large field enhancement at the Ångström level. Although it is very difficult to directly characterize the atomistic structures of the tip, the Raman scattering from the apex’s own vibrations of the metal tip can provide valuable information about the stacking of atoms at the tip apex. However, conventional quantum chemistry packages can only simulate the Raman scattering of small metal clusters with few atoms due to huge computational cost, which is not enough since the shaft of the tip behind the apex also makes significant contributions to the polarizabilities of the whole tip. Here we propose an atomistic polarization model to simulate the Raman spectra of large metal tips at subwavelength scales based on the combination of the atomistic discrete dipole approximation model and the density functional theory. The atomistic tip with different sizes and stacking structures is considered in its entirety during the calculation of polarizabilities, and only the vibrational contributions from the tip apex are taken into account to simulate the Raman spectra of the tip. The Raman spectral features are found to be very sensitive to the local constituent element at the tip apex, atomic stacking modes, and shape of the tip apex, which can thus be used as a fingerprint to identify different atomistic structures of the tip apex. Moreover, our approaches can be extended to the metal tips with sub-wavelength sizes, making it possible to consider both the large scale and the atomistic detail of the tip simultaneously. The method presented here can be used as a basic tool to simulate the Raman scattering process of the metal tips and other nanostructures in an economic way, which is beneficial for understanding the roles of atomistic structures in tip- and surface-enhanced spectroscopies.

Metasurface characterization based on eigenmode analysis and averaging of electromagnetic fields

A fully numerical homogenization technique for the retrieval of the effective surface susceptibilities of a periodic composite metasurface is developed in this work. We utilize the so-called dual field-flux finite element formulation scheme to accurately calculate the eigenmodes of a composite periodic metasurface, a scheme that possesses a crucial advantage: The capability of evaluating all field components and their derivatives accurately and with the same order of approximation is a requirement for our proposed technique. Next, we derive the generalized sheet transition condition equations for a general bianisotropic metasurface, which correlate the field components on either sides of the metasurface with its surface susceptibilities. At this point, we establish a new field averaging scheme for the acquisition of the average field components of the modes supported by the metasurface. Combining this computational information, we derive a set of linear algebraic equations based on the GSTCs and the average electromagnetic fields and numerically solve it, so as to obtain the effective surface susceptibilities of a bianisotropic metasurface. Comparison with the results of other techniques in the literature shows very good agreement, relatively to the resonance behavior of the returned values and their position at the frequency spectrum. The advantages that distinguish the proposed technique over other related methods are its foundation on the intrinsic modal information of the eigenmodes supported by the metasurface and its independence of any wave excitation schemes or involvement of analytical polarizability calculations.

Comparison between PBE-D3, B3LYP, B3LYP-D3 and MP2 Methods for quantum mechanical calculations of polarizability and IR-NMR spectra in C24 isomers, including a novel isomer with D2d symmetry

In this study, we have performed a comprehensive theoretical analysis of C24 isomers in the gaseous phase using the PBE-D3/cc-pVTZ, B3LYP/cc-pVTZ, B3LYP-D3/cc-pVTZ and MP2/6-31G methods. We have also considered the basis set cc-pVTZ for the MP2 method, and carried out optimized (single point) calculations in three isomers (in the remaining two isomers where the convergence was too time consuming) in order to reveal the potentiality of the method. Our investigation covered a wide range of properties, including geometry optimizations, chemical stability, polarizabilities, nuclear screening constants, Fermi (FE), gap (GE) and atomization energies (AE), thermodynamic analysis, reactivity index, as well as IR and NMR spectra. These calculations were performed for the ring (D12h), sheet (D6h) and two cage (D6d and Oh) configurations. Interestingly, we also proposed a new structure, the bracelet (D2d) arrangement, which appeared to be stable according to the PBE, B3LYP and B3LYP-D3 methods, but was classified as a transition state by the MP2 method. The results consistently indicated that the D6h isomer is the most stable one among the C24 isomers studied, while the D2d isomer was found to be the least stable. Regarding the gap energy (GE), the B3LYP and B3LYP-D3 methods consistently yielded higher values compared to the PBE’s, with an average DFT (PBE and B3LYP) GE of 1.89 eV, whereas the MP2 method showed a substantially higher GE value of 7.6 eV, representing an increase of approximately 75%. Additionally, the polarizabilities of the C24 isomers were found to be overestimated by the PBE, B3LYP and B3LYP-D3 methods when compared to the corresponding MP2 values. The PBE-D3 method consistently produced higher polarizabilities for the C24 isomers in comparison to the B3LYP, B3LYP-D3 and MP2 methods. The investigation confirms that the Oh (D12h) isomer has the smallest (largest) polarizability, as agreed upon by all methods. Moreover, the polarizability of D12h is notably affected by the selected DFT method, while that of Oh displays lower sensitivity but shares similarities with D6d. However, for the newly proposed D2d isomer, the polarizability is ranked third (fourth) in ascending order with the PBE-D3 (B3LYP-D3) method. This highlights the importance of considering the electronic correlation and dispersion effects in accurately predicting polarizabilities. The results obtained from the different methods shed light on the impact of the methodology choice on the predicted properties, emphasizing the need for careful consideration when analyzing and interpreting theoretical results for such various geometries.

Polarization consistent dielectric screening in polarizable continuum model calculations of solvation energies.

A polarization consistent framework, where dielectric screening is affected consistently in polarizable continuum model (PCM) calculations, is employed for the study of solvation energies. The computational framework combines a screened range-separated-hybrid functional (SRSH) with PCM calculations, SRSH-PCM, where dielectric screening is imposed in both PCM self-consistent reaction field (SCRF) iterations and the electronic structure Hamiltonian. We begin by demonstrating the impact of modifying the Hamiltonian to include such dielectric screening in SCRF iterations by considering the solutions of electrostatically embedded Hartree-Fock (HF) exact exchange equations. Long-range screened HF-PCM calculations are shown to capture properly the linear dependence of gap energy of frontier orbitals on the inverse of the dielectric constant, whereas unscreened HF-PCM orbital energies are fallaciously semi-constant with respect to the dielectric constant and, therefore, inconsistent with the ionization energy gaps. Similar trends affect density functional theory (DFT) calculations that aim to achieve predictive quality. Importantly, the dielectric screened calculations are shown to significantly affect DFT- and HF PCM-based solvation energies, where screened solvation energies are smaller compared to the unscreened values. Importantly, SRSH-PCM, therefore, appears to reduce the tendency of DFT-PCM to overestimate solvation energies, where we find the effect to increase with the dielectric constant and the polarity of the molecular solute, trends that enhance the quality of DFT-PCM calculations of solvation energy. Understanding the relationship of dielectric screening in the Hamiltonian and DFT-PCM calculations can ultimately benefit on-going efforts for the design of predictive and parameter free descriptions of solvation energies.

Photoelectron Spectroscopy of Oppositely Charged Molecular Switches in the Aqueous Phase: Theory and Experiment.

XUV photoelectron spectroscopy (XPS) is a powerful method for investigating the electronic structures of molecules. However, the correct interpretation of results in the condensed phase requires theoretical models that account for solvation. Here we present experimental aqueous-phase XPS of two organic biomimetic molecular switches, NAIP and p-HDIOP. These switches are structurally similar, but have opposite charges and thus present a stringent benchmark for solvation models which need to reproduce the observed ΔeBE = 1.1 eV difference in electron binding energy compared to the 8 eV difference predicted in the gas phase. We present calculations using implicit and explicit solvent models. The latter employs the average solvent electrostatic configuration and free energy gradient (ASEC-FEG) approach. Both nonequilibrium polarizable continuum models and ASEC-FEG calculations give vertical binding energies in good agreement with the experiment for three different computational protocols. Counterions, explicitly accounted for in ASEC-FEG, contribute to the stabilization of molecular states and reduction of ΔeBE upon solvation.

Theoretical investigation on corrosion inhibition efficiency of some amino acid compounds

The DFT approach was used to do quantum chemical calculations of amino acids energy, geometrical shape, and optoelectronic properties. The investigation of the optoelectronic properties of the substance under consideration is focused on its UV–vis spectra. The calculation of dipole moment, polarizability, hardness, softness, ionization potential, electronegativity, electrophilicity, nucleophilicity, electron transfer, back-donation energy, and first-order static hyperpolarizability at the DFT/B3LYP/6-311++G(d,p) level of theory revealed the underlying molecule's nonlinear optical behavior. To further elucidate the compound's molecular properties, frontier molecular orbitals, and molecular electrostatic potential maps were provided. At different temperatures, the chemical reactivity and thermodynamic characteristics of amino acids were determined. The computed HOMO and LUMO energies demonstrated that the charge transfer takes place within the molecule. Studies have shown that higher EHOMO values result in higher electron donation, and ELUMO values determine the ability to receive electrons. The order of corrosion inhibition efficiency is determined by the band gap energy of the inhibitor, and a larger band gap results in the poorest corrosion inhibitor. The heteroatoms such as nitrogen, oxygen, sulfur, and phosphorus in an inhibitor structure leads to stronger inhibition when adsorbed onto a metal surface. The selected molecules studied in this work have charge transfer properties towards mild steel, and their inhibition efficiency increases as the electron-donating ability increases. The maximum amount of negative-adsorption energy indicates the best inhibitor for corrosion, with the ranking of identified substances being 3-(((2-methyl-4-nitrophenyl)amino)methyl)phenol(D) > 2-((2-hydroxy-5-methoxybenzylidene)amino) pyridine(C) > 3-(((2,4-dinitrophenyl)imino)methyl)phenol (F) > 2-[(methylamino)methyl]pyridine (E) > l-Tryptophan(B) > l-Histidine(A).