scholarly journals Water Interaction with Fe2NiP Schreibersite (110) Surface: a Quantum Mechanical Atomistic Perspective

Author(s):  
Stefano Pantaleone ◽  
Marta Corno ◽  
Albert Rimola ◽  
Nadia Balucani ◽  
Piero Ugliengo

Phosphorus is an element of primary importance for all living creatures, being present in many biological activities in the form of phosphate (PO43-). However, there are still open questions about the origin of this specific element and on the transformation which allowed it to be incorporated in biological systems. The most probable source of prebiotic phosphorus is the intense meteoritic bombardment during the Archean era, few million years after the solar system formation, which brought tons of iron-phosphide materials (schreibersite) on the early Earth crust. It was recently demonstrated that by simple wetting/corrosion processes from this material various oxygenated phosphorus compounds are produced. In the present work, the wetting process of schreibersite (Fe2NiP) was studied by computer simulations using density functional theory, with the PBE functional supplemented with dispersive interactions through a posteriori empirical correction. To start disentangling the complexity of the system, only the most stable (110) surface of Fe2NiP was used simulating different water coverages, from which structures, water binding energies and vibrational spectra have been predicted. The computed (ana-)harmonic infrared spectra have been compared with the experimental ones, thus confirming the validity of the adopted methodology and models.

2021 ◽  
Vol 7 (7) ◽  
pp. 101
Author(s):  
Ian Shuttleworth

A comparative study of the unreacted and reacted uniaxially strained Pt(111) and the layered (111)-Pt/Ni/Pt3Ni and (111)-Pt/Ni/PtNi3 surfaces has been performed using density functional theory (DFT). An in-depth study of the unreacted surfaces has been performed to evaluate the importance of geometric, magnetic and ligand effects in determining the reactivity of these different Pt surfaces. An analysis of the binding energies of oxygen and hydrogen over the high-symmetry binding positions of all surfaces has been performed. The study has shown that O and H tend to bind more strongly to the (111)-Pt/Ni/Pt3Ni surface and less strongly to the (111)-Pt/Ni/PtNi3 surface compared to binding on the equivalently strained Pt(111) surfaces. Changes in the surface magnetisation of the surfaces overlaying the ferromagnetic alloys during adsorption are discussed, as well as the behaviour of the d-band centre across all surfaces, to evaluate the potential mechanisms for these differences in binding. An accompanying comparison of the accessible density functionals has been included to estimate the error in the computational binding energies.


2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.


2010 ◽  
Vol 21 (12) ◽  
pp. 1469-1477 ◽  
Author(s):  
M. SAMAH ◽  
B. BOUGHIDEN

Structures, binding energies, magnetic and electronic properties endohedrally doped C 20 fullerenes by metallic atoms ( Fe , Co , Ti and V ) have been obtained by pseudopotential density functional theory. All M @ C 20, except Co @ C 20, are more stable than the undoped C 20 cage. The magnetic moment values are 1 and 2μB. These values and semiconductor behavior give to these compounds interesting feature in several technological applications. Titanium doped C 20 has a same magnetic moment than the isolated Ti atom. Hybridization process in the Co doped C 20 fullerene is most strong than in other doped cages. Electrical and magnetic dipoles calculated in the iron doped C 20 are very strong compared with other clusters.


2013 ◽  
Vol 205-206 ◽  
pp. 417-421
Author(s):  
Tatsunori Yamato ◽  
Koji Sueoka ◽  
Takahiro Maeta

The lowest energetic configurations of metal impurities in 4throw (Sc - Zn), 5throw (Y - Cd) and 6throw (Hf - Hg) elements in Ge crystals were determined with density functional theory calculations. It was found that the substitutional site is the lowest energetic configuration for most of the calculated metals in Ge. The most stable configurations of dopant (Ga, Sb) - metal complexes in Ge crystals were also investigated. Following results were obtained. (1) For Ga dopant, 1st neighbor T-site is the most stable for metals in group 3 to 7 elements while substitutional site next to Ga atom is the most stable for metals in group 8 to 12 elements. (2) For Sb dopant, substitutional site next to Sb atom is the most stable for all calculated metals. Binding energies of the interstitial metalMiwith the substitutional dopantDswere obtained by the calculated total energies. The calculated results for Ge were compared with those for Si.


2013 ◽  
Vol 321-324 ◽  
pp. 499-502
Author(s):  
Hong Zhou ◽  
Jun Feng Wang ◽  
Jun Qing Wen ◽  
Wei Bin Cheng ◽  
Jun Fei Wang

Density-functional theory has been used to calculate the energetically global-minimum geometries and electronic states of AgnH2S (n=2, 4, 6) clusters. The lowest-energy structures of Ag2, Ag4, Ag6, Ag2H2S, Ag4H2S and Ag6H2S clusters were obtained, respectively. The calculation results show that the lowest-energy structures of Ag2, Ag4and Ag6clusters are planar geometries. The binding energies of Agn(n=2, 4, 6) clusters are gradually increasing in our calculations. Compare the infrared spectrum peaks of Ag4cluster with that of Ag6cluster, which show that the peaks shift to shortwave. After adsorption, we found that the peaks shift to shortwave by comparison.


2021 ◽  
Author(s):  
Ian Murphy ◽  
Peter Rice ◽  
Madison Monahan ◽  
Leo Zasada ◽  
Elisa Miller ◽  
...  

Covalent functionalization of Ni2P nanocrystals was demonstrated using aryl-diazonium salts. Spontaneous adsorption of aryl functional groups was observed, with surface coverages ranging from 20-96% depending on the native reactivity of the salt as determined by the aryl substitution pattern. Increased coverage was possible for low reactivity species using a sacrificial reductant. Functionalization was confirmed using thermogravimetric analysis, FTIR and X-ray photoelectron spectroscopy. The structure and energetics of this nanocrystal electrocatalyst system, as a function of ligand coverage, was explored with density functional theory calculations. The Hammett parameter of the surface functional group was found to linearly correlate with the change in Ni and P core-electron binding energies and the nanocrystal’s experimentally and computationally determined work-function. The electrocatalytic activity and stability of the functionalized nanocrystals for hydrogen evolution were also improved when compared to the unfunctionalized material, but a simple trend based on electrostatics was not evident. We used density functional theory to understand this discrepancy and found that H adsorption energies on the covalently functionalized Ni2P also do not follow the electrostatic trend and are predictive descriptors of the experimental results.


2019 ◽  
Vol 42 (1) ◽  
pp. 143-149 ◽  
Author(s):  
Özgür Alver ◽  
Cemal Parlak ◽  
Yunusa Umar ◽  
Ponnadurai Ramasami

Abstract Fullerenes have received attentions due to their versatile properties. Molecular structures and electronic properties namely binding energy, band gap, electrophilicity index and molecular topological analysis were studied for undoped and silicon doped C20 fullerenes and favipiravir in order to search for possible application of the systems as drug delivery vehicles. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) were used for the research. Molecular structures having the interaction edges of SiC19… OH in water and SiC19…C=O in gas phase were found as those most stable with binding energies of -57.28 kcal/mol and -43.46 kcal/mol correspondingly. The results and parameters found in this research may provide additional insights into drug delivery systems.


2019 ◽  
Vol 33 (29) ◽  
pp. 1950347 ◽  
Author(s):  
Xiao-Chong Liang ◽  
Xiao-Jiang Long ◽  
Lin Zhang ◽  
Jun Zhu

The structural and electronic transport properties of [Formula: see text] clusters are studied based on density functional theory (DFT). Their most stable structures are proved to be planar by the particle swarm optimization (PSO) algorithm, and have decreasing binding energies with the increasing number of Ga atom in clusters. The electronic transport properties of these clusters connected with two Al(1 0 0) electrodes are calculated by combining nonequilibrium Green’s-function (NEGF) with DFT. Most of them have an equilibrium conductance of above [Formula: see text], except for [Formula: see text]. Negative differential resistance (NDR) phenomenon of different level is observed in their I–V curves in bias ranges of from [Formula: see text] to [Formula: see text] V and from 0.7 to 1.1 V.


Author(s):  
Quintin Hill ◽  
Chris-Kriton Skylaris

While density functional theory (DFT) allows accurate quantum mechanical simulations from first principles in molecules and solids, commonly used exchange-correlation density functionals provide a very incomplete description of dispersion interactions. One way to include such interactions is to augment the DFT energy expression by damped London energy expressions. Several variants of this have been developed for this task, which we discuss and compare in this paper. We have implemented these schemes in the ONETEP program, which is capable of DFT calculations with computational cost that increases linearly with the number of atoms. We have optimized all the parameters involved in our implementation of the dispersion correction, with the aim of simulating biomolecular systems. Our tests show that in cases where dispersion interactions are important this approach produces binding energies and molecular structures of a quality comparable with high-level wavefunction-based approaches.


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