Stability of Adsorbed Water on TiO2-TiN Interfaces. A First Principles and Ab Initio Thermodynamics Investigation.

2018 ◽  
Author(s):  
Michael Nolan ◽  
Julio Gutierrez ◽  
Pierre Loverra ◽  
Marco Fronzi ◽  
Alan O'Riordan
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Adsorbed Water ◽  
Free Energy Calculations ◽  
Ambient Conditions ◽  
High Concentration ◽  
High Coverage ◽  
Reducing Conditions ◽  
Atomistic Thermodynamics ◽  
The Stability

Titanium Nitride (TiN) surfaces can oxidise and the growth of a TiO<sub>x</sub> layer on the surface along with the likely presence of water in the surrounding environment can modify the properties of this widely used coating material. The present Density Functional Theory study, including Hubbard +U correction (DFT+U), investigates the stability of adsorbed water at TiO<sub>2</sub>-TiN interfaces with different defects, that serve as a model for an oxide layer grown on a TiN surface. Surface free energy calculations show the stability of perfect TiN-TiO<sub>2</sub> interface at regular O pressures, while oxygen vacancy-rich TiO<sub>1.88</sub>–TiN is more favourable at reducing conditions. An isolated water is preferentially adsorbed dissociatively at perfect and oxygen defective interfaces while molecular adsorption is more stable at higher coverages. The adsorption energy is stronger at the oxygen defective interfaces which arises from the high concentration of reduced Ti<sup>3+</sup> and strong interfacial atomic relaxations. Ab initio atomistic thermodynamics show that water will be present at high coverage on TiO<sub>2</sub>-TiN interfaces at ambient conditions and the pristine interface is only stable at very low pressure of O and H<sub>2</sub>O. The results of these DFT+U simulations are important for the fundamental understanding of wettability of interfacial systems involving metal oxides.

Stability of Adsorbed Water on TiO2-TiN Interfaces. A First Principles and Ab Initio Thermodynamics Investigation.

2018 ◽  
Author(s):  
Michael Nolan ◽  
Julio Gutierrez ◽  
Pierre Loverra ◽  
Marco Fronzi ◽  
Alan O'Riordan
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Adsorbed Water ◽  
Free Energy Calculations ◽  
Ambient Conditions ◽  
High Concentration ◽  
High Coverage ◽  
Reducing Conditions ◽  
Atomistic Thermodynamics ◽  
The Stability

Titanium Nitride (TiN) surfaces can oxidise and the growth of a TiO<sub>x</sub> layer on the surface along with the likely presence of water in the surrounding environment can modify the properties of this widely used coating material. The present Density Functional Theory study, including Hubbard +U correction (DFT+U), investigates the stability of adsorbed water at TiO<sub>2</sub>-TiN interfaces with different defects, that serve as a model for an oxide layer grown on a TiN surface. Surface free energy calculations show the stability of perfect TiN-TiO<sub>2</sub> interface at regular O pressures, while oxygen vacancy-rich TiO<sub>1.88</sub>–TiN is more favourable at reducing conditions. An isolated water is preferentially adsorbed dissociatively at perfect and oxygen defective interfaces while molecular adsorption is more stable at higher coverages. The adsorption energy is stronger at the oxygen defective interfaces which arises from the high concentration of reduced Ti<sup>3+</sup> and strong interfacial atomic relaxations. Ab initio atomistic thermodynamics show that water will be present at high coverage on TiO<sub>2</sub>-TiN interfaces at ambient conditions and the pristine interface is only stable at very low pressure of O and H<sub>2</sub>O. The results of these DFT+U simulations are important for the fundamental understanding of wettability of interfacial systems involving metal oxides.

Structure, Stability and Water Adsorption on Ultra-Thin TiO2 Supported on TiN

2019 ◽  
Author(s):  
Jose Julio Gutierrez Moreno ◽  
Marco Fronzi ◽  
Pierre Lovera ◽  
alan O'Riordan ◽  
Mike J Ford ◽  
...  
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Chemical Potential ◽  
Energy Gap ◽  
Molecular Water ◽  
Structure Stability ◽  
Ambient Conditions ◽  
Rutile Structure ◽  
The Stability ◽  
The One

<p></p><p>Interfacial metal-oxide systems with ultrathin oxide layers are of high interest for their use in catalysis. In this study, we present a density functional theory (DFT) investigation of the structure of ultrathin rutile layers (one and two TiO<sub>2</sub> layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti–O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti<sup>3+</sup> cations in TiO<sub>2.</sub> The structure of the one-layer oxide slab is strongly distorted at the interface, while the thicker TiO<sub>2</sub> layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly non-stoichiometric interfaces. Isolated water molecules dissociate when adsorbed at the TiO<sub>2</sub> layers. At higher coverages the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. Interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. A water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO<sub>1.75</sub>-TiN interface, where the Ti<sup>3+</sup> states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO<sub>2</sub>-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultrathin TiO<sub>2</sub> with potential application as photocatalytic water splitting devices.</p><p></p>

scholarly journals Ab initio study of elastic anisotropies and thermal conductivities of rhenium diborides in different crystal structures

RSC Advances ◽  
2020 ◽  
Vol 10 (61) ◽  
pp. 37142-37152
Author(s):  
Yi X. Wang ◽  
Ying Y. Liu ◽  
Zheng X. Yan ◽  
W. Liu ◽  
Jian B. Gu
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Crystal Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Ab Initio Study ◽  
Ambient Conditions ◽  
Functional Theory ◽  
Thermal Conductivities

The phase stabilities, elastic anisotropies, and thermal conductivities of ReB2 diborides under ambient conditions have been investigated by using density functional theory calculations.

scholarly journals Ab initio thermodynamics of liquid and solid water

2019 ◽  
Vol 116 (4) ◽  
pp. 1110-1115 ◽  
Author(s):  
Bingqing Cheng ◽  
Edgar A. Engel ◽  
Jörg Behler ◽  
Christoph Dellago ◽  
Michele Ceriotti
Keyword(s):  
Machine Learning ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Machine Learning Techniques ◽  
Intermediate Step ◽  
Hybrid Functional ◽  
Learning Techniques ◽  
The Stability ◽  
Comprehensive Framework

Thermodynamic properties of liquid water as well as hexagonal (Ih) and cubic (Ic) ice are predicted based on density functional theory at the hybrid-functional level, rigorously taking into account quantum nuclear motion, anharmonic fluctuations, and proton disorder. This is made possible by combining advanced free-energy methods and state-of-the-art machine-learning techniques. The ab initio description leads to structural properties in excellent agreement with experiments and reliable estimates of the melting points of light and heavy water. We observe that nuclear-quantum effects contribute a crucial 0.2 meV/H2O to the stability of ice Ih, making it more stable than ice Ic. Our computational approach is general and transferable, providing a comprehensive framework for quantitative predictions of ab initio thermodynamic properties using machine-learning potentials as an intermediate step.

Structure, Stability and Water Adsorption on Ultra-Thin TiO2 Supported on TiN

2019 ◽  
Author(s):  
Jose Julio Gutierrez Moreno ◽  
Marco Fronzi ◽  
Pierre Lovera ◽  
alan O'Riordan ◽  
Mike J Ford ◽  
...  
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Chemical Potential ◽  
Energy Gap ◽  
Molecular Water ◽  
Structure Stability ◽  
Ambient Conditions ◽  
Rutile Structure ◽  
The Stability ◽  
The One

<p></p><p>Interfacial metal-oxide systems with ultrathin oxide layers are of high interest for their use in catalysis. In this study, we present a density functional theory (DFT) investigation of the structure of ultrathin rutile layers (one and two TiO<sub>2</sub> layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti–O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti<sup>3+</sup> cations in TiO<sub>2.</sub> The structure of the one-layer oxide slab is strongly distorted at the interface, while the thicker TiO<sub>2</sub> layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly non-stoichiometric interfaces. Isolated water molecules dissociate when adsorbed at the TiO<sub>2</sub> layers. At higher coverages the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. Interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. A water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO<sub>1.75</sub>-TiN interface, where the Ti<sup>3+</sup> states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO<sub>2</sub>-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultrathin TiO<sub>2</sub> with potential application as photocatalytic water splitting devices.</p><p></p>

Ab-initio DFT simulation of electronic and magnetic properties of Tin+1and FeTin clusters

2021 ◽  
Author(s):  
Rachida Haichour ◽  
Sofiane MAHTOUT
Keyword(s):  
Magnetic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Three Dimensional ◽  
Binding Energies ◽  
Chemical Hardness ◽  
Generalized Gradient ◽  
Cage Structure ◽  
Electronic And Magnetic Properties ◽  
The Stability

Abstract We report a computational investigation of the electronic and magnetic properties of neutral Tin+1and FeTin (n=1-10) clusters using ab-initio calculations based on density functional theory (DFT) within the generalized gradient approximation (GGA). The best structures for Tin+1and FeTin clusters are planar for size n<5, while from n = 5, they showed a compact three dimensional cage structure. For the best structures of the FeTin clusters, the Fe atoms favors the peripheral position with highest coordination with the neighboring Ti atoms. The evolution as a function of the size of the average binding energies (Eb/atom) and HOMO–LUMO gaps of Tin+1 and FeTin (n=1-10) clusters are studied. The stability results show that the Tin+1 clusters have relatively higher stability than the FeTin cluster with the same size. In addition, the vertical ionization potentials and electron affinities, chemical hardness and atomic magnetic moment of Tin+1and FeTin (n=1-10) clusters are also investigated.

High coverage adsorption and co-adsorption of CO and H2 on Ru(0001) from DFT and thermodynamics

2015 ◽  
Vol 17 (29) ◽  
pp. 19446-19456 ◽  
Author(s):  
Peng Zhao ◽  
Yurong He ◽  
Dong-Bo Cao ◽  
Xiaodong Wen ◽  
Hongwei Xiang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Co Adsorption ◽  
High Coverage ◽  
Functional Theory ◽  
Adsorption Of Co ◽  
Atomistic Thermodynamics

The adsorption and co-adsorption of CO and H2 at different coverages on p(4 × 4) Ru(0001) have been computed using periodic density functional theory (GGA-RPBE) and atomistic thermodynamics.

Ab initio density functional studies on the stability of tetrathiocyanato complexes of Zn(II), Cd(II) and Hg(II)

1997 ◽  
Vol 255 (1) ◽  
pp. 211-214 ◽  
Author(s):  
Nobuhiro Fukushima ◽  
Gouichi Iisaka ◽  
Masahiko Saito ◽  
Kenji Waizumi
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Functional Studies ◽  
The Stability

scholarly journals Investigation of the structural and electronic properties of CdS under high pressure: an ab initio study

2018 ◽  
Vol 96 (2) ◽  
pp. 216-224 ◽  
Author(s):  
C. Yamcicier ◽  
Z. Merdan ◽  
C. Kurkcu
Keyword(s):  
Phase Transition ◽  
Ab Initio ◽  
Density Functional ◽  
Structural Phase ◽  
Type Structure ◽  
Ambient Conditions ◽  
Space Group ◽  
Space Groups ◽  
Intermediate States ◽  
Calculation Results

An ab initio constant pressure study is carried out to explore the behaviour of cadmium sulfide (CdS) under high hydrostatic pressure. We have studied the structural properties of CdS using density functional theory (DFT) under pressure up to 200 GPa. CdS crystallizes in a wurtzite (WZ)-type structure under ambient conditions. CdS undergoes a structural phase transition from the hexagonal WZ-type structure with space group P63mc to cubic NaCl-type structure with space group [Formula: see text]. Another phase transition is obtained from NaCl-type structure to the orthorhombic CdS-III-type structure with space group Pmmn. The first transformation proceeds via seven intermediate states with space group Cmc21, P21, Pmn21, P21/m, Pmmn, I4/mmm, and Cmcm. The latter transformation is based on two intermediate states with space groups Immm and P21/m. These phase transitions are also studied by total energy and enthalpy calculations. According to these calculations, the phase transformations occur at about 3 and 51 GPa, respectively. Calculation results on the other basic properties, such as lattice constant, volume, and bulk modulus are also compared with those of other recent theoretical and experimental data, and generally, good agreement with the available data are obtained.

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