scholarly journals Water Adsorption on the β-Dicalcium Silicate Surface from DFT Simulations

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 386 ◽  
Author(s):  
Qianqian Wang ◽  
Hegoi Manzano ◽  
Iñigo López-Arbeloa ◽  
Xiaodong Shen
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Lone Pair ◽  
Dicalcium Silicate ◽  
Atomic Scale ◽  
Partial Density ◽  
Key Factor ◽  
Charge Analysis ◽  
Adsorption Energies ◽  
Oxygen Lone Pair

β-dicalcium silicate (β-Ca2SiO4 or β-C2S in cement chemistry notation) is one of the most important minerals in cement. An improvement of its hydration rate would be the key point for developing environmentally-friendly cements with lower energy consumption and CO2 emissions. However, there is a lack of fundamental understanding on the water/β-C2S surface interactions. In this work, we aim to evaluate the water adsorption on three β-C2S surfaces at the atomic scale using density functional theory (DFT) calculations. Our results indicate that thermodynamically favorable water adsorption takes place in several surface sites with a broad range of adsorption energies (−0.78 to −1.48 eV) depending on the particular mineral surface and adsorption site. To clarify the key factor governing the adsorption of the electronic properties of water at the surface were analyzed. The partial density of states (DOS), charge analysis, and electron density difference analyses suggest a dual interaction of water with a β-C2S (100) surface including a nucleophilic interaction of the water oxygen lone pair with surface calcium atoms and an electrophilic interaction (hydrogen bond) of one water hydrogen with surface oxygen atoms. Despite the elucidation of the adsorption mechanism, no correlation was found between the electronic structure and the adsorption energies.

scholarly journals Water Adsorption on the β-Dicalcium Silicate Surface from DFT Simulations

2018 ◽  
Author(s):  
Qianqian Wang ◽  
Hegoi Manzano ◽  
Iñigo López-Arbeloa ◽  
Xiadong Shen
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Lone Pair ◽  
Dicalcium Silicate ◽  
Atomic Scale ◽  
Partial Density ◽  
Key Factor ◽  
Charge Analysis ◽  
Adsorption Energies ◽  
Oxygen Lone Pair

β-dicalcium silicate (β-Ca2SiO4, or β-C2S in cement chemistry notation) is one of the most important minerals in cement. An improvement of its hydration rate would be the key point for developing environmentally friendly cements with lower energy consumption and CO2 emissions. However, there is a lack of fundamental understanding on the water/β-C2S surface interactions. In this work we aim to evaluate the water adsorption on three β-C2S surfaces at the atomic scale using density functional theory (DFT) calculations. Our results indicate that thermodynamically favorable water adsorption takes place in several surface sites, with a broad range of adsorption energies (−0.78 to −1.48 eV), depending on the particular mineral surface and adsorption site. To clarify the key factor governing the adsorption, the electronic properties of water at the surface were analyzed. The partial density of states (DOS), charge analysis, and electron density difference analyses suggest a dual interaction of water with β-C2S (100) surface: a nucleophilic interaction of the water oxygen lone pair with surface calcium atoms, and an electrophilic interaction (hydrogen bond) of one water hydrogen with surface oxygen atoms. Despite the elucidation of the adsorption mechanism, no correlation was found between the electronic structure and the adsorption energies.

scholarly journals Water Adsorption on the β-Dicalcium Silicate Surface from DFT Simulations: a Dual Nucleophilic-Electrophilic Interaction

2018 ◽  
Author(s):  
Qianqian Wang ◽  
Hegoi Manzano ◽  
Iñigo López-Arbeloa ◽  
Xiadong Shen
Keyword(s):  
Density Functional ◽  
Structural Changes ◽  
Water Adsorption ◽  
Lone Pair ◽  
Dicalcium Silicate ◽  
Partial Density ◽  
Surface Sites ◽  
Key Factor ◽  
Charge Analysis ◽  
Oxygen Lone Pair

β-dicalcium silicate (β-Ca2SiO4, or β-C2S in cement chemistry notation) is one of the most important minerals in cement. An improvement of its hydration speed would be the key point for developing environmentally friendly cements with lower energy consumption and CO2 emissions. However, there is a lack of fundamental understanding on the water/β-C2S surface interactions. Therefore, in this work we aim to understand the water adsorption and dissociation mechanism on the β-C2S (100) surface using density functional theory (DFT) calculations. Our results indicate that thermodynamically favorable water adsorption process takes place in several surface sites, with a broad range of adsorption energies (-0.78 to -1.24 eV), depending on the particular water conformation and surface site. To clarify the key factor governing the adsorption, the electronic properties of water at the surface sites were analyzed. The partial density of states (DOS), charge analysis, and electron density difference analyses suggest a dual interaction of water with β-C2S (100) surface: a nucleophilic interaction of the water oxygen lone pair with surface calcium atoms, and an electrophilic interaction (hydrogen bond) of one water hydrogen with surface oxygen atoms, being the first one the stronger interaction. Hence, we suggest that β-C2S hydration could be enhanced by introducing chemical or structural changes that increase both the electronegative/positive character of the surface.

scholarly journals Unsaturated and Benzannulated N-Heterocyclic Carbene Complexes of Titanium and Hafnium: Impact on Catalysts Structure and Performance in Copolymerization of Cyclohexene Oxide with CO2

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4364
Author(s):  
Lakshmi Suresh ◽  
Ralte Lalrempuia ◽  
Jonas B. Ekeli ◽  
Francis Gillis-D’Hamers ◽  
Karl W. Törnroos ◽  
...  
Keyword(s):  
Density Functional ◽  
Lone Pair ◽  
Catalytic Performance ◽  
Nbo Analysis ◽  
Cyclohexene Oxide ◽  
Group 4 ◽  
Low Co2 ◽  
And Performance ◽  
High Yields ◽  
Oxygen Lone Pair

Tridentate, bis-phenolate N-heterocyclic carbenes (NHCs) are among the ligands giving the most selective and active group 4-based catalysts for the copolymerization of cyclohexene oxide (CHO) with CO2. In particular, ligands based on imidazolidin-2-ylidene (saturated NHC) moieties have given catalysts which exclusively form polycarbonate in moderate-to-high yields even under low CO2 pressure and at low copolymerization temperatures. Here, to evaluate the influence of the NHC moiety on the molecular structure of the catalyst and its performance in copolymerization, we extend this chemistry by synthesizing and characterizing titanium complexes bearing tridentate bis-phenolate imidazol-2-ylidene (unsaturated NHC) and benzimidazol-2-ylidene (benzannulated NHC) ligands. The electronic properties of the ligands and the nature of their bonds to titanium are studied using density functional theory (DFT) and natural bond orbital (NBO) analysis. The metal–NHC bond distances and bond strengths are governed by ligand-to-metal σ- and π-donation, whereas back-donation directly from the metal to the NHC ligand seems to be less important. The NHC π-acceptor orbitals are still involved in bonding, as they interact with THF and isopropoxide oxygen lone-pair donor orbitals. The new complexes are, when combined with [PPN]Cl co-catalyst, selective in polycarbonate formation. The highest activity, albeit lower than that of the previously reported Ti catalysts based on saturated NHC, was obtained with the benzannulated NHC-Ti catalyst. Attempts to synthesize unsaturated and benzannulated NHC analogues based on Hf invariably led, as in earlier work with Zr, to a mixture of products that include zwitterionic and homoleptic complexes. However, the benzannulated NHC-Hf complexes were obtained as the major products, allowing for isolation. Although these complexes selectively form polycarbonate, their catalytic performance is inferior to that of analogues based on saturated NHC.

scholarly journals Density Functional Theory Study Of The Interaction Of Hydroxyl Groups With Iron Surface

2015 ◽  
Vol 60 (2) ◽  
pp. 931-933 ◽  
Author(s):  
N. Nunomura ◽  
S. Sunada
Keyword(s):  
Density Functional Theory ◽  
Iron Atom ◽  
Density Functional ◽  
Lone Pair ◽  
Hydroxyl Groups ◽  
Electronic Interaction ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Surface Iron ◽  
Adsorption Energies

AbstractThe electronic interaction of hydroxyl groups with Fe(100) surface is modelled using a density functional theory (DFT) approach. The adsorption energies and structures of possible adsorption sites are calculated. According to our calculations of the adsorption energies, the interaction between oxygen atom of OH species and surface iron atom is shown to be strong. It is likely to be due to the interaction of the lone-pair electrons of oxygen and the 3dorbital electrons of iron atom. At low coverage (0.25ML), the most favorable adsorption sites are found to be two-fold bridge sites, and the orientation of the O-H bond is tilted to the surface normal. Further, the adsorption energy is found to be decreasing with the increasing OH group coverage.

scholarly journals Crystal Structures, Surface Stability, and Water Adsorption Energies of La-Bastnäsite via Density Functional Theory and Experimental Studies

2016 ◽  
Vol 120 (30) ◽  
pp. 16767-16781 ◽  
Author(s):  
Sriram Goverapet Srinivasan ◽  
Radha Shivaramaiah ◽  
Paul R. C. Kent ◽  
Andrew G. Stack ◽  
Alexandra Navrotsky ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Crystal Structures ◽  
Density Functional ◽  
Water Adsorption ◽  
Experimental Studies ◽  
Functional Theory ◽  
Surface Stability ◽  
Adsorption Energies

Comparison of X12Y12 (X=Al, B and Y=N, P) fullerene-like nanoclusters toward adsorption of dimethyl ether

2018 ◽  
Vol 17 (02) ◽  
pp. 1850013 ◽  
Author(s):  
Ali Shokuhi Rad
Keyword(s):  
Electronic Structure ◽  
Dimethyl Ether ◽  
Density Functional ◽  
Binding Energies ◽  
Frontier Molecular Orbital ◽  
Functional Theory ◽  
Charge Analysis ◽  
Adsorption Energies ◽  
P Type ◽  
Semiconducting Property

Density functional theory (DFT) was used for studying the adsorption of dimethyl ether (DME) onto four nanoclusters: [Formula: see text] ([Formula: see text], B and [Formula: see text], P). The interaction energy along with the adsorption energy was investigated, and it was found that DME molecule has higher binding energies upon adsorption on Al-containing clusters, but on the other hand, it results in higher alteration in the electronic structure of B-containing cluster. Outcomes of charge analysis and frontier molecular orbital confirm higher alteration in the electronic structure of the later clusters, suggesting the possible potential of B[Formula: see text]N[Formula: see text] and B[Formula: see text]P[Formula: see text] as two sensitive sensors for DME. Nevertheless, Al-containing clusters showed much better adsorbent property, judging from their higher adsorption energies. The positive values of charge transfer upon DME adsorption confirm the p-type semiconducting property of all these clusters.

scholarly journals Visible Light-Induced Homolytic Cleavage of Perfluoroalkyl Iodides Mediated by Phosphines

Molecules ◽  
2020 ◽  
Vol 25 (7) ◽  
pp. 1606 ◽  
Author(s):  
Mario Bracker ◽  
Lucas Helmecke ◽  
Martin Kleinschmidt ◽  
Constantin Czekelius ◽  
Christel M. Marian
Keyword(s):  
Visible Light ◽  
Density Functional ◽  
Experimental Studies ◽  
Lone Pair ◽  
Functional Theory ◽  
Computational Evaluation ◽  
Light Region ◽  
Condon Factors ◽  
Oxygen Lone Pair ◽  
Franck Condon

In an effort to explain the experimentally observed variation of the photocatalytic activity of t Bu 3 P, n Bu 3 P and (MeO) 3 P in the blue-light regime [Helmecke et al., Org. Lett. 21 (2019) 7823], we have explored the absorption characteristics of several phosphine– and phosphite–IC 4 F 9 adducts by means of relativistic density functional theory and multireference configuration interaction methods. Based on the results of these computational and complementary experimental studies, we offer an explanation for the broad tailing of the absorption of t Bu 3 P-IC 4 F 9 and (MeO) 3 P-IC 4 F 9 into the visible-light region. Larger coordinate displacements of the ground and excited singlet potential energy wells in n Bu 3 P-IC 4 F 9 , in particular with regard to the P–I–C bending angle, reduce the Franck–Condon factors and thus the absorption probability compared to t Bu 3 P-IC 4 F 9 . Spectroscopic and computational evaluation of conformationally flexible and locked phosphites suggests that the reactivity of (MeO) 3 P may be the result of oxygen lone-pair participation and concomitant broadening of absorption. The proposed mechanism for the phosphine-catalyzed homolytic C–I cleavage of perfluorobutane iodide involves S1 ← S0 absorption of the adduct followed by intersystem crossing to the photochemically active T 1 state.

Adsorption and Diffusion of Magnesium on Nitrogen Doped Mo2C Monolayer

2021 ◽  
Author(s):  
Jiangfeng Ni ◽  
Kaimin Fan ◽  
Jing Tang
Keyword(s):  
Density Functional ◽  
Nitrogen Doping ◽  
Partial Density ◽  
Fast Diffusion ◽  
Functional Theory ◽  
Nitrogen Doped ◽  
Lower Energy Level ◽  
Adsorption Energies ◽  
And Diffusion ◽  
Diffusion Behaviors

Abstract The Mg adsorption and diffusion behaviors on nitrogen doped (N-doped) Mo2C monolayer have been systematically investigated by the first principles based on density functional theory (DFT). The adsorption energies of Mg on pristine Mo2C and Mo2C1 − xNx (x = 0.0625, 0.125, 0.1875 and 0.25) have been studied. The adsorption energies of Mg on N-doped Mo2C are lower than that of pristine Mo2C. Especially, the adsorption energies of Mg are − 1.639 eV and − 1.625 eV on TC1 and H2 sites for Mo2C0.875N0.125, which have decreased by 16.49% and 18.43%. Furthermore, the Mg diffuses along H3-B-H4 and H-B-H with the barriers of 0.021 eV and 0.028 eV, which indicate that Mo2C0.875N0.125 exhibits fast diffusion properties. Additionally, the partial density of states (PDOS) reveals the interaction between Mg and Mo2C0.875N0.125. The PDOS results indicate that nitrogen doping causes the PDOS peaks transfer to a lower energy level, which is benefit for the bonding between Mg and MoC0.875N0.125. These results suggest that the adsorption and diffusion behaviors of Mg are enhanced by nitrogen doping.

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

2017 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Metal Ions ◽  
Bond Length ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Oxygen Lone Pair

Bond-length distributions are examined for thirty-three configurations of the metalloid ions and fifty-six configurations of the post-transition-metal ions bonded to oxygen. Lone-pair stereoactivity is discussed.

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

2017 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Metal Ions ◽  
Bond Length ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Oxygen Lone Pair

Bond-length distributions are examined for thirty-three configurations of the metalloid ions and fifty-six configurations of the post-transition-metal ions bonded to oxygen. Lone-pair stereoactivity is discussed.

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