Effective Core Potential Basis Sets Research Articles

The surface chemistry of norbornadiene and norbornene on Pd(111) and Pd(100): a comparative DFT study.

The interaction of norbornadiene (NBD) and norbornene (NBE) with the palladium (111) and (100) surfaces have been investigated using density functional theory (DFT). Five configurations of adsorbed NBD may be formed on Pd(111): endo-tetra-σ, endo-di-σ,π, endo-di-π, exo-di-σ, and exo-π. The NBE molecule adsorbed on Pd(111) may exist in 4 configurations: endo-di-σ, endo-π, exo-di-σ, and exo-π. On Pd(100), a smaller number adsorption configurations of NBD and NBE are formed, since the double bonds of these molecules in the endo-orientation are bound only in a di-σ mode. The adsorption energy of NBD and NBE molecules on Pd(100) is noticeably higher compared to Pd(111), which is due to the surface geometry of Pd(100). The most stable configurations on both Pd facets are endo-tetra-σ for NBD and exo-di-σ for NBE. However, due to smaller adsorption area of the exo-di-σ configuration on Pd(111), a larger number of NBD molecules may adsorbed on the same surface area. Energetically favorable endo-tetra-σ (NBD) and exo-di-σ (NBE) configurations are very mobile on Pd(111). On Pd(100), only NBE molecules can migrate, while NBD migration is hindered due to the high activation barrier. All DFT calculations were performed using the Perdew-Burke-Ernzerhof density functional (PBE) with the relativistic SBK effective core potential and TZ2P basis set in the PRIRODA program.

Failure of effective core potential (ECP) basis sets in excited state optimization of complex containing Hg2+ ion

Failure of effective core potential (ECP) basis sets in excited state optimization of complex containing Hg2+ ion

Synthesis, Crystal Structure, Hirshfeld Surfaces Analysis, Interaction with DNA and Comparation of Different Bases in Hirshfeld Atom Refinement of New Polymorph of Chlorido(η6-p-cymene)(diclofenac)Ruthenium(II) Organometallic Compound

A new polymorph of the ruthenium(II) diclofenac complex with formula [Ru(p-cymene)(diclo)Cl] was synthesized, and its crystal structure was solved by single crystal X-ray diffraction. The structure was refined by HAR, using five different relativistic bases sets (x2c-SVP, jorge-DZP-DKH, jorge-TZP-DKH, x2c-TZVP, and x2c-TZVPP) and three effective core potential basis sets (ECP-def2-SVP, ECP-def2-TZVP, and ECP-def2-TZVPP). Their influence on the structure parameters was compared. The analysis of the supramolecular structure of the HAR/non-HAR structures, as well as of the orthorhombic polymorph, was supported by the calculation and analysis of the Hirshfeld surfaces. The best results were observed for HAR using triple-zeta-based sets. No significant effect of base choice on Hirshfeld surfaces was observed. A study of the ability of the complex to interact with ct-DNA was also performed. The complex was shown to interact with ct-DNA, but the mode of interaction is not fully elucidated.

Quantum Dynamics and Bi Metal Force Field Parameterization Yielding Significant Antileishmanial Targets.

Amid emerging drug resistance to metal inhibitors, high toxicity, and onerous drug delivery procedures, the computational design of alternate formulations encompassing functional metal-containing compounds greatly relies on large-scale atomistic simulations. Simulations particularly with Au(I), Ag, Bi(V), and Sb(V) pose a major challenge to elucidate their molecular mechanism due to the absence of force field parameters. This study thus quantum mechanically derives force field parameters of Bi(V) as an extension of the previous experimental study conducted on heteroleptic triorganobismuth(V) biscarboxylates of type [BiR3(O2CR')2]. We have modeled two organo-bismuth(V) carboxylates, which are optimized and parameterized along with the famous pentavalent antimonial drug: meglumine antimoniate using quantum mechanics original Seminarian methods with the SBKJC effective core potential (ECP) basis set. Furthermore, molecular dynamics (MD) simulations of bismuth- and antimony-containing compounds in complex with two enzymes, trypanothione synthetase-amidase (TSA) and trypanothione reductase, are performed to target the (T(SH)2) pathway at multiple points. MD simulations provide novel insights into the binding mechanism of TSA and highlight the role of a single residue Arg569 in modulating the ligand dynamics. Moreover, the presence of an ortho group in a ligand is emphasized to facilitate interactions between Arg569 and the active site residue Arg313 for higher inhibitory activity of TSA. This preliminary generation of parameters specific to bismuth validated by simulations in replica will become a preamble of future computational and experimental research work to open avenues for newer and suitable drug targets.

An examination of the reaction pathways of XO + O → X + O2 (X = Br and I)

Kinetics and mechanism of potentially important atmospheric ozone depletion reactions XO + O → X + O2 (X = Br and I) have been explored at the ab initio level. Several minimum energy geometries and transition states are identified at the MP2 level using correlation consistent triple zeta and effective core potential basis sets and energetics are obtained at the QCISD(T)//MP2 level of theory. Possible reaction pathways are discussed on the basis of IRC calculations and changes of geometries along the reaction paths. A direct reaction mechanism as well as reaction path via transition states and equilibrium geometries are identified. For both the reactions, early transition states have been detected just after the reactions start. In case of BrO + O reaction, we obtained a transition state of Br.OO type before the product formation, whereas in case of IO + O reaction, an equilibrium geometry of I.OO type has been detected leading to the product formation. Similar to I.OO, for ClO + O reaction an equilibrium geometry of Cl.OO type was reported in literature for product formation. This anomaly for TS-Br.OO may be due the artifact of MP2 optimization method. A multi-reference approach is expected to reveal the correct picture. A detailed dynamical study of this transition state may lead to clear bond-breaking and bond-forming information, which may be helpful to predict the true reaction pathway. Heats of reaction are found to be consistent with experimental data. Bond dissociation energies of the ground state intermediate isomers to various dissociation asymptotes are also reported. This is the first theoretical report for the possible reaction pathways and may be served as a reference for future investigation using higher methodology.

Computational Study on Vibrational Properties of Thyroxine Molecule in Different Charge States

The vibrational frequencies of thyroxine (T4) molecule are calculated through computational method and major modes of vibration are assigned to corresponding frequencies in this research work. First we took neutral isolated T4 molecule for our study, and then we extend our work to anion state. The shift produced in the frequency and IR intensities for different vibrational modes has been calculated for change in state from neutral to anion. In addition, the difference spectra for these two charge states has also been studied for the T4 molecule by adding the dimethyl sulfoxide (DMSO) solvent. Furthermore, the same calculations are performed for the isolated neutral T4 molecule with C13 labelling. All these calculations are carried out by density functional calculations with the B3LYP hybrid functional applying the SDD effective core potential basis set. The calculated geometrical parameters are in good agreement with the experimental results. Additionally, the calculated frequencies lies within the characteristic region belonging to the respective mode of vibrations.

Theoretical investigation on the reaction mechanism of ozone with chlorine, bromine and iodine atoms

Theoretical investigation on the reaction mechanism of X + O3 → XO + O2 (X = Cl, Br and I) reactions have been performed at the ab initio level using correlation consistent and effective core potential basis sets. The geometry and frequency of the reactants, products, equilibrium geometries and transition states are obtained using MP2 level of theory and energetics are calculated at the CCSD(T) and QCISD(T) methods. Heat of reactions are found to be consistent with the experimental data. Possible reaction pathways are discussed. In case of reactions of ozone with chlorine and brome, it starts producing a nonplanar trioxide (OOOX) transition state with acute dihedral angle. It then proceeds via nonplanar equilibrium geometry and transition state. Finally dissociates to XO + O2 from a planar O2·OX equilibrium geometry. For the reaction with iodine, initial transition state and equilibrium geometry with acute dihedral angle are disappeared. The reaction proceeds through planar intermediates and finally dissociated to IO + O2 via O2·OI isomer. There exists a flat plateau on the potential energy surface in the intermediate region for all the cases. Finding of O2·OX equilibrium geometry strengthens the suggestion of previous investigations and for the possibility of direct reaction mechanism. High level theoretical investigation including reaction dynamics on these reactions can reveal the actual reaction mechanism.

A DFT/EDA study of ethanol decomposition over Pt, Cu and Rh metal clusters

Ethanol reforming has emerged in the last decades as a powerful solution for the energy problem, providing a way for hydrogen production from a renewable and environmentally friendly source. In the search for the best catalyst for this process, it is crucial to understand the reaction mechanism in all its details. In this work, we compare the reaction mechanism for the ethanol decomposition over Pt, Cu and Rh. The approach presented here involves the use of metal clusters treated by effective core potential basis set and the remaining species treated with all electrons. DFT calculations (B3LYP-D3) were used to construct the potential energy surface for all the steps in the path from ethanol to CH4, CH3CH3 and CH2CH2. Canonical molecular orbital energy decomposition analysis (CMOEDA) was used to understand the distinct behavior of the three metals. After the formation of acetaldehyde, the reaction over Pt and Rh easily continues towards the C–C bond breaking, which is much more difficult for Cu. The better capability of Pt and Rh to stabilize transition states is, in most cases, explained by a more malleable electron density in these clusters. This malleability allows the clusters to adjust the electron density to better deal with charge transfers taking place throughout every reaction step.

The geometric and spectroscopic features of (CuSe)n = 2–8 binary nanoclusters: a theoretical study

Based on the density functional theory (DFT) and time-dependent (TD) DFT methods, the geometric and spectroscopic features of (CuSe)n = 2–8 binary nanoclusters were systematically studied, and five kinds of isomers are obtained as local minima structures at each cluster size. The BHandH hybrid functional and effective core potential basis set LanL2DZ are used for copper atoms. The triple-ζ valence plus polarization basis set TZVP is selected for selenium atoms. For each cluster size, the relative energies of these five stable isomers are evaluated for the conformational isomerization. There are significant differences in infrared spectra between the isomeric structures, and the infrared spectra bands distinctly show differences in the low-frequency region between smaller size clusters and higher size clusters. The higher molar absorption coefficient is consistent with UV-Vis spectroscopy in the wavelength range of 200~400 nm. The calculated UV-Vis spectra clearly show that all clusters exhibit permissible excited electronic transitions in the range 0~10 eV. Therefore, these clusters can be used as potential UV-absorbing materials due to their strong UV absorption.

Accurate theoretical method for homolytic cleavage of C[sbnd]Sn bond: A benchmark approach

Stille coupling is a well-known cross coupling reaction, where the rate determination step is the dissociation of carbon stannous (CSn) bond. The organotin compounds are also used as precursors in the manufacturing of tin oxide films, solar cells, gas sensors, flat panel display technology and low emission glass materials, etc. The reactivity of organotin compounds has direct relationship with the homolytic cleavage of CSn bond. Therefore, accurate determination of CSn bond has direct relevance in understanding many phenomena. The current benchmark study is aimed at finding out the accurate theoretical method for the homolytic cleavage (bond dissociation energy) of CSn bond. In this regard, nineteen DFs from eight different classes of DFT with two effective core potential basis sets (LANL2DZ and SDD) and two Karlsruhe basis sets (def2-SVP and def2-TZVP) are selected for the BDE calculation of CSn bond. Ten structurally diverse organotin compounds with experimentally known BDE of CSn bond are selected from the literature. The statistical [root mean square deviation (RMSD), standard deviation (SD), Pearson’s correlation (R) and mean absolute error (MAE)] results are obtained by the comparison of theoretical data with the experimental BDE values of CSn bond of selected organotin compounds. Among all DFT classes, GGA-D class is a batter class and BLYP-D3 functional of this class is selected as the best functional for homolytic bond dissociation energy (BDE) calculation of CSn bond. This functional with SDD basis set shows remarkable performance in reproducing the BDE of CSn bond with more accuracy. The SD, RMSD, R and MAE are 4.11 kcal mol−1 is 3.9 kcal mol−1 is 0.963 and −0.01 kcal mol−1, respectively.

High level ab initio thermochemistry of XeF radical

Thermodynamic characteristics of XeF2 stepwise defluorination reaction have been studied using sophisticated methods of quantum chemistry. The set of standard enthalpies of formation for the XeF2-related intermediates (radicals, ions) was obtained using approximation of coupled clusters level of theory [CCSD(T)/complete basis set extrapolation] with Peterson’s effective core potential correlation consistent basis sets for Xe. The standard enthalpy of formation for xenon monofluoride radical was determined to be ΔfH°(XeF) = 15.4 kcal mol−1 (298 K). The radical is formed in the first step of XeF2 homolytic decomposition which requires 59.7 kcal mol−1. The second step (XeF dissociation) is characterized by an extremely low binding energy (BDE(XeF) = 3.1 kcal mol−1) explaining the high fluorinating potential of the xenon difluoride. An interpretation of low XeF stability was given in terms of MO – AO correlation diagrams. It was shown that the electronic structure of XeF radical may be described as combination of two main configurations, the first of them has a canonical set of MOs with single-occupied HOMO of antibonding character, whereas the second configuration is characterized by low-lying SOMO with main contributions from 5S AO of Xe and 2pz AO of fluorine.

Molecular Structure, Electronic Structure, Properties and Analyses of Five Azopyridine Ruthenium Complexes α-Cl, β-Cl, γ-Cl, δ-Cl and ε-Cl of RuCl<sub>2</sub>(4,6-Dimethyl-Phenylazopyridine)<sub>2</sub> as Potential Cancer Drugs: DFT and TD-DFT Investigations

Ground state geometries, natural bond orbital (NBO), analysis of frontier molecular orbitals (FMOs), analysis and spectral (RMN and UV-Visible) properties of five azopyridine ruthenium (II) complexes α-Cl, β-Cl, γ-Cl, δ-Cl and e-Cl of RuCl2(Dazpy)2 have been theoretically studied by the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods using two basis sets: Lanl2DZ and a generic basis set in gas or in chloroform solvent. Dazpy stands for 4,6-dimethyl-phenylazopyridine. Optimized geometry shows that, except β-Cl, all the other four isomers α-Cl, γ-Cl, δ-Cl and e-Cl are C2 symmetrical. Otherwise, a good agreement was found between experimental and the calculated geometry and NMR data. Moreover, Lanl2DZ effective core potential basis set provides good chemical shifts and geometric properties. Furthermore, the prediction of the frontier orbitals (Highest Occupied Molecular Orbital or HOMO and Lowest Unoc-cupied Molecular Orbital or LUMO) shows that the most active isomer suita-ble for electronic reactions is admitted to be δ-Cl. Besides, the NBO analysis indicates that the Ru-N is formed by the electron delocalization of lone pair atomic orbital of N2 and Npy to Ru. Also, the strongest interactions between LP(N) with LP*(Ru) and LP(Cl) with LP*(Ru) stabilize the molecular struc-ture. In addition, NBO shows that the five d orbitals of Ru in the complex are organized so that there is no order of priority from one complex to another. Therefore, the transition LP(Ru) → π*(N1 = N2) corresponding to Metal to Li-gand Charge Transfer (MLCT) is in reality no more than d → π*. Besides, TDDFT prediction in chloroform solvent reveals that all the five isomerics complexes absorb in the visible region as well as efficient photosensitizers. What’s more, δ-RuCl2(dazpy)2 can potentially act as the excellent sensitizer with a large band of absorption in visible region and a small excited energy. This study can help design and find out the ability or properties of the com-plex to behave as sensitizer or potential cancer drugs.

Noble gas cluster ions

In this work, a reaction mechanism of formation of noble gas (Ng) cluster ions has been theoretically investigated in detail. The kinetic studies of formation of Xe+Xe cluster in Xe, Ar+Ar cluster ions in Ar, and Ne+Ne cluster ions in Ne have been made as theoretically. The optimized structures in the ground state were calculated using the density functional theory (DFT) by the B3LYP method combined with the Stuttgart/Dresden effective core potential basis set (SDD). In addition, we calculated the rate constants of all cluster formations. The results are 1.15 × 10−31, 3.58 × 10−31, 0.23 × 10−31cm6/s, respectively for Neon, Argon, Xenon cluster ions.

Computational Study on Reduction Potential of [CoP4N2(OH2)2]2+ as a Super-Efficient Catalyst in Electrochemical Hydrogen Evolution

Hydrogen is considered as a unique choice for future world’s resources. The important parameter in the process of hydrogen production is the value of reduction potential for the used catalyst, in direct contact with consumed energy in process. The application of computational methods to design and modify molecular catalysts is highly regarded. This study sought to explore Density Functional Theory (DFT), employing an effective core potential basis set (LanL2DZ) for metals, as an applicable method used to calculate molecular geometries and electronic structures of the redox forms of two new super-efficient catalysts, CoP4N2 and FeP4N2. The reduction potential related to CoP4N2 catalyst in the presence of water solvent is measured using a reference isodesmic reaction. The calculated data revealed that obtained theoretical value for the reduction potential of catalyst, -0.58V, is in an excellent agreement with its experimental value, -0.50 V. The results confirmed that water molecules coordinated with Co or Fe core in catalyst structure play the main role in H2 gas production.

In Situ-Raman Spectroscopy and Comparison with DFT Computational and Experimental Study of Electroless Nickel Deposition

The kinetic mechanism of the electroless deposition of NiP from hypophosphite solutions was investigated from first principles with the intent of determining a set of elementary reactions that could effectively identify the most relevant steps of this complex process. The outcome of the computational approach is discussed in terms of experimental results obtained by electrochemical methods and surface analysis techniques [1,2]. Simulations were performed with Density Functional Theory DFT using the B3LYP exchange and correlation functionals [3], the 6-311+G(d,p) basis set for P,C,H and O atoms [4], and the Stuttgart effective core potential basis sets for Ni [5]). The interaction of Ni++ and H2PO2- with the Ni surface was studied using Ni clusters of different sizes (from 4 to 12 atoms). Solvation in water was modeled using the implicit polarizable continuum model [6]; calculations were performed using the G09 computational suite [7]. Simulations were initially devoted to the identification of the first reaction steps that lead to the adsorption of Ni++ on the Ni surface and to its successive reduction by means of the hypophosphite anion. Though several theories were proposed to describe this key step in the literature, our search was guided by the original insight published several years ago [8], according to which the reduction of Ni++ requires the formation of an intermediate species containing the NiOH group. Such species would then take active part in the transfer of the OH group to H2PO2-, thus favoring its oxidation to H2PO3-. In addition, it was imposed that the searched elementary mechanism satisfies the experimental observation, obtained with marked deuterium species, that each molecule of hydrogen that is evolved contextually to the deposition of NiP contains two H atoms coming from two H2PO2- anions. The possibility that NiOH+ is formed in solution prior to deposition was investigated determining computationally the pKa of Ni++. Results revealed that the formation of NiOH+ is not favored in the pH ranges in which NiP is usually deposited. A similar result was obtained when considering the possibility that NiOH+, after being formed in solution, is stabilized through the formation of a complex with H2PO2-. A thermodynamically favored set of reactions was instead found when it was investigated the possibility that NiOH is formed at the surface contextually with a Ni-H2PO2 complex. It was in fact found that the following set of reactions has a globally slightly negative (≈ -5 ± 5 kcal/mol) free energy change: R1) Ni ++ + surf ® Niads ++ R2) Niads ++ + 2 H2O + H2PO2 - ® NiOH(H2PO2)ads + H3O+ The minimum energy structure of the surface NiOH(H2PO2)ads species optimized at the B3LYP level on a Ni8 cluster in implicit water. The two reactions set R1-R2 provides a mechanism for the initial step of reduction of Ni++, thermodynamically viable and consistent with the hypotheses formulated above. The results of this analysis suggest therefore that the initial step of Ni++ reduction during NiP deposition involves a concerted mechanism in which adsorbed Ni++ contextually reacts with H2PO2- and a water molecule. This mechanism can be also supported by electrochemical measurements, indicating the need of OH funtionalization of the catalytic surface in order to have the reaction of hyposphite. In order to understand completely the adsorption phenomena on the electrode surface during the electroless deposition process, in situ-Raman analyses were performed. The purpose of this experimental section is to discern the different complexes adsorbed on the electrode surface while the reaction proceeds. These tests were carried out at different temperature, starting from the ambient temperature to the effective process temperature. The effect of each complexing agent dissolved into electroless NiP bath on complexes adsorbed on the electrode surface and the comparison with the DFT computational analysis will be presented.

Synthesis and use of α-aminophosphine oxides and N,N-bis(phosphinoylmethyl)amines – A study on the related ring platinum complexes

The Kabachnik–Fields condensation was extended using secondary phosphine oxides, such as dibenzylphosphine oxide and bis(4-methylphenyl)phosphine oxide as the P-reactant in reaction with formaldehyde and different primary amines. Besides the α-aminophosphine oxides, the corresponding bisproducts, N,N-bis(phosphinoylmethyl)amines were also synthesized under appropriate conditions. The bis(phosphinoyl)amines were then converted to ring platinum complexes after double deoxygenation. The substituent dependence of the energetics of the complexation reaction using bidentate P-ligands, and the stereostructure of a few complexes were evaluated by B3LYP/6-31G(d,p) calculations using the effective core potential (ECP) basis set (SDD). The crystal structure of a few ring Pt species was studied by X-ray analysis. Catalytic activity of the complexes synthesized was investigated in hydroformylation.

A High-Precision Calculation of Bond Length and Spectroscopic Constants of Hg2 Based on the Coupled-Cluster Theory with Spin—Orbit Coupling**Supported by the Start-Up Funds of Xi'an Polytechnic University under Grant No BS1211, and the Scientific Research Program Funded by Shaanxi Provincial Education Department under Grant No 2013JK0679.

Based on the two-component relativistic effective core potential and matched basis sets cc-pwcvnz-pp (n=Q, 5), combining the completed basis-set extrapolation of electronic correlation energy and the fourth-order polynomial fitting technique, the bond length and spectroscopic constants of Hg2 are studied by the coupled cluster theory with spin—orbit coupling. Spin—orbit coupling is included in the post Hartree—Fock procedure, i.e., in the coupled-cluster iteration, to obtain more reliable theoretical results. The results show that our theoretical values agree with the experimental values very well and will be helpful to understand the spectral character of Hg2.

NCI analysis of the interaction cation⋯π in complexes with molecular bowls derived from fullerene

A systematic study based on the non-covalent interactions (NCI) index was carried out in order to analyze the characteristics of the cation⋯π interaction in complexes formed by alkaline cations (Li+, Na+, K+, Rb+, and Cs+) and molecular bowls of increasing size, going from corannulene, C20H10, to the fully closed buckminsterfullerene, C60. For this purpose all the possible inner complexes with the cation on the bottom of the bowl were studied. SCF densities were employed at the B3LYP/6-31+G∗ level (LANL2DZ effective core potential basis set was included for Rb+ and Cs+). NCI plots allowed to visualize the characteristics of the cation⋯π interaction; showing the spatial arrangement of the interaction and locating the regions of different interaction strength. Moreover, when the comparison of NCI plot is carried out in an adequate way, an excellent correlation with the calculated complexation energies was found. Finally, in order to obtain complementary data, QTAIM calculations were carried out for several complexes, locating critical points and bond paths.

Investigation of the initial steps of the electrochemical reduction of CO2 on Pt electrodes.

The initial steps of the electrochemical reduction of CO2 at Pt electrodes were computationally investigated at the molecular level. Simulations were performed with density functional theory using the B3LYP functional and effective core potential basis sets. The surface was modeled through two clusters comprising 13 and 20 atoms. An implicit solvation model was used to describe solvation effects for two different solvents: water and acetonitrile. It was found that CO2 adsorption is highly favored on negatively charged clusters and takes place passing from a well-defined transition state. The computational evidence suggests that the electrodic CO2 adsorption reaction may be described as a concerted process in which an electron-transfer reaction takes place contextually to CO2 adsorption. Also, the present results suggest that the formation of the CO2(•–) aqueous species is significantly unfavored from an energetic standpoint and that its main fate, if formed, would be most likely that of getting adsorbed again on the Pt surface. The calculation of the pKa of adsorbed CO2(–) showed that its protonation reaction is thermodynamically favored in most electrochemical conditions used for CO2 reduction. Also, it was found that the free-energy difference between adsorbed formate and adsorbed COOH favors the latter, suggesting that the interconversion kinetics of these two species at a Pt surface may play an important role in determining the system reactivity. A tentative global mechanism able to describe the CO2 reactivity on Pt surfaces is proposed.

DFT Computational and Experimental Study of Electroless Nickel Deposition

The kinetic mechanism of the electroless deposition of NiP from hypophosphite solutions was investigated from first principles with the intent of determining a set of elementary reactions that could effectively identify the most relevant steps of this complex process. The outcome of the computational approach is discussed in terms of experimental results obtained by electrochemical methods and surface analysis techniques [1,2]. The computational study was performed without considering explicitly the effect that complexing agents introduced in solution may have on the deposition kinetics. Simulations were performed with Density Functional Theory DFT using the B3LYP exchange and correlation functionals [3], the 6-311+G(d,p) basis set for P,C,H and O atoms [4], and the Stuttgart effective core potential basis sets for Ni [5]). The interaction of Ni++ and H2PO2- with the Ni surface was studied using Ni clusters of different sizes (from 4 to 12 atoms). Solvation in water was modeled using the implicit polarizable continuum model [6]; calculations were performed using the G09 computational suite [7]. Simulations were initially devoted to the identification of the first reaction steps that lead to the adsorption of Ni++ on the Ni surface and to its successive reduction by means of the hypophosphite anion. Though several theories were proposed to describe this key step in the literature, our search was guided by the original insight published several years ago [8,9], according to which the reduction of Ni++ requires the formation of an intermediate species containing the NiOH group. Such species would then take active part in the transfer of the OH group to H2PO2-, thus favoring its oxidation to H2PO3-. In addition, it was imposed that the searched elementary mechanism satisfies the experimental observation [10], obtained with marked deuterium species, that each molecule of hydrogen that is evolved contextually to the deposition of NiP contains two H atoms coming from two H2PO2- anions. The possibility that NiOH+ is formed in solution prior to deposition was investigated determining computationally the pKa of Ni++. Results revealed that the formation of NiOH+ is not favored in the pH ranges in which NiP is usually deposited. A similar result was obtained when considering the possibility that NiOH+, after being formed in solution, is stabilized through the formation of a complex with H2PO2-. A thermodynamically favored set of reactions was instead found when it was investigated the possibility that NiOH is formed at the surface contextually with a Ni-H2PO2 complex. It was in fact found that the following set of reactions has a globally slightly negative (≈ -5 ± 5 kcal/mol) free energy change: R1) Ni ++ + surf --> Niads ++ R2) Niads ++ + 2 H2O + H2PO2 - --> NiOH(H2PO2)ads + H3O+ The two reactions set R1-R2 provides a mechanism for the initial step of reduction of Ni++, thermodynamically viable and consistent with the hypotheses formulated above. The results of this analysis suggest therefore that the initial step of Ni++ reduction during NiP deposition involves a concerted mechanism in which adsorbed Ni++ contextually reacts with H2PO2- and a water molecule. This mechanism can be also supported by electrochemical measurements, indicating the need of OH funtionalization of the catalytic surface in order to have the reaction of hyposphite. References P.L. Cavallotti, L. Magagnin, Influence of added elements on ACD electroless NiP, ECS Transactions, 50 (53) 1-8 (2013).P.L. Cavallotti, L. Magagnin, C. Cavallotti, Influence of added elements on autocatalytic chemical deposition electroless NiP, Electrochim. Acta (2013), http://dx.doi.org/10.1016/j.electacta.2013.09.083.A. D. Becke, J. Chem. Phys. 98, 1372. (1993), C.T. Lee, W.T. Yang, R. G. Parr, Phys. Rev. B, 37, 785 (1988).K. Raghavachari, J. S. Binkley, R. Seeger, and J. A. Pople, J. Chem. Phys. 72, 650 (1980).P. Fuentealba, H. Preuss, H. Stoll, L.v. Szentpaly, Chem. Phys. Lett., 89, 418 (1982).B. Mennucci, E. Cances, J. Tomasi, J. Phys. Chem. B 101, 10506 (1997).M. J. Frisch et al., Gaussian 09, Revision A.1; Gaussian, Inc.: Wallingford CT, 2009.P. Cavallotti, G. Salvago, Electrochimica Metallorum III, 239 (1968).G. Salvago, P.L. Cavallotti, Plating, 59(7), 665 (1972).A.A. Sutyagina, K.M. Gorbunova, P.M. Glazunov, Dokl. Ak. NAUK SSSR, 147, 1133 (1962).