Boron and indium substitution in GaAs(001) surfaces: Density-functional supercell calculations of the surface stability

2007 ◽  
Vol 601 (4) ◽  
pp. 900-907 ◽  
Author(s):  
Arndt Jenichen ◽  
Cornelia Engler
Keyword(s):  
Density Functional ◽  
Surface Stability

Molecular Dynamic Structure Investigations of the Surface Stability and Adsorption of H, H2, CH3, C2H2: (100) Diamond

1992 ◽  
Vol 270 ◽  
Author(s):  
Th. Frauenheim ◽  
P. Blaudeck ◽  
D. Porezag
Keyword(s):  
Density Functional ◽  
Dynamic Structure ◽  
Md Simulations ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Minimal Basis ◽  
Surface Stability ◽  
Hydrogen Supply ◽  
Reaction Processes ◽  
Structure Investigations

ABSTRACTSurface properties - stability and reconstruction - of clean and hydrogenated diamond (100) have been studied by real temperature molecular dynarnic (MD) simulations using an approximate density functional (DF) theory expanding the total electronic wave function in a minimal basis of localized atomic valence electron orbitals (LCAO - ansatz). The clean surface is highly unstable against a spontaneous dimerization resulting in a 2×1 reconstruction. Atomic hydrogen in the gas phase above the top surface at all temperatures and H2 molecules approaching the center of the dimer bond at room temperature are reactive in breaking the dimer π-bonds forming a monohydrogenated surface which maintains a stable 2×1 structure but with elongated surface C-C dimer bonds remaining stable against continuing hydrogen supply. The dihydrogenated surface taking a 1×1 structure, because of steric overcrowding dynamically becomes unstable against forming a 1×1 (alternating) di-, monohydrogenated surface. As first elementary reaction processes which may be discussed in relation to diamond growth we studied the thermal adsorption of CH3 and C2H2 onto a clean 2×l reconstructed (100) diamond surface.

Influence of Carbon Dioxide on the Energetics of Cerium Oxide Surfaces and Nanoparticle Morphology

2020 ◽  
Author(s):  
Adam Symington ◽  
Robert M. Harker ◽  
Mark T. Storr ◽  
Marco Molinari ◽  
Stephen Charles Parker
Keyword(s):  
Carbon Dioxide ◽  
Cerium Oxide ◽  
Density Functional ◽  
Surface Oxidation ◽  
Pressure Change ◽  
Surface Stability ◽  
Nanoparticle Morphology ◽  
External Conditions ◽  
Temperature And Pressure ◽  
The Stability

Many nanoparticles show enhanced catalytic activity on particular surfaces. Hence, a key challenge is to identify strategies to control the expression of such surfaces and to avoid their disappearance over time. Here, we use density functional theory to explore the adsorption of carbon dioxide on the surfaces of Cerium oxide (CeO<sub>2</sub>), and its relationship with the resulting nanoparticle morphology under conditions of pressure and temperature.<b> </b>CeO<sub>2</sub> is an important solid electrolyte in fuel cells, a catalyst, and enzyme mimetic agent in biomedicine, and has been shown to interact strongly with CO<sub>2</sub>. We demonstrate that the adsorption of CO<sub>2</sub> as a carbonate ion is energetically favorable on the {111}, {110} and {100} surfaces of CeO<sub>2</sub>, and that the strength of this interaction is morphology and surface stoichiometry dependent. By predicting the surface stability as a function of temperature and pressure, we built surface phase diagrams and predict the surface dependent desorption temperatures of CO<sub>2</sub>. These temperatures of desorption follow the order {100} > {110} > {111} and are higher for surfaces containing oxygen vacancies compared to stoichiometric surfaces, indicating that surface oxidation processes can reduce the stability of surface carbonate groups. Finally, we propose a thermodynamic strategy to predict the evolution of nanoparticle morphology in the presence of CO<sub>2</sub> as the external conditions of temperature and pressure change. We show that there is a thermodynamic driving force dependent on CO<sub>2</sub> adsorption that should be considered when selecting nanoparticle morphologies in catalytic applications.

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

Surface stability of potassium nitrate (KNO3) from density functional theory

2010 ◽  
Vol 50 (2) ◽  
pp. 356-362 ◽  
Author(s):  
O.M. Løvvik ◽  
T.L. Jensen ◽  
J.F. Moxnes ◽  
O. Swang ◽  
E. Unneberg
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Potassium Nitrate ◽  
Functional Theory ◽  
Surface Stability

Nitrogen substitutions in GaAs(001) surfaces: Density-functional supercell calculations of the surface stability

2005 ◽  
Vol 242 (14) ◽  
pp. 2820-2832 ◽  
Author(s):  
Arndt Jenichen ◽  
Cornelia Engler ◽  
Gunnar Leibiger ◽  
Volker Gottschalch
Keyword(s):  
Density Functional ◽  
Surface Stability

scholarly journals Thermodynamic Evolution of Cerium Oxide Nanoparticle Mor-phology using Carbon Dioxide.

2020 ◽  
Author(s):  
Adam Symington ◽  
Robert M. Harker ◽  
Mark T. Storr ◽  
Marco Molinari ◽  
Stephen Charles Parker
Keyword(s):  
Carbon Dioxide ◽  
Cerium Oxide ◽  
Density Functional ◽  
Surface Oxidation ◽  
Pressure Change ◽  
Surface Stability ◽  
Nanoparticle Morphology ◽  
External Conditions ◽  
Temperature And Pressure ◽  
The Stability

Many nanoparticles show enhanced catalytic activity on particular surfaces. Hence, a key challenge is to identify strategies to control the expression of such surfaces and to avoid their disappearance over time. Here, we use density functional theory to explore the adsorption of carbon dioxide on the surfaces of Cerium oxide (CeO<sub>2</sub>), and its relationship with the resulting nanoparticle morphology under conditions of pressure and temperature.<b> </b>CeO<sub>2</sub> is an important solid electrolyte in fuel cells, a catalyst, and enzyme mimetic agent in biomedicine, and has been shown to interact strongly with CO<sub>2</sub>. We demonstrate that the adsorption of CO<sub>2</sub> as a carbonate ion is energetically favorable on the {111}, {110} and {100} surfaces of CeO<sub>2</sub>, and that the strength of this interaction is morphology and surface stoichiometry dependent. By predicting the surface stability as a function of temperature and pressure, we built surface phase diagrams and predict the surface dependent desorption temperatures of CO<sub>2</sub>. These temperatures of desorption follow the order {100} > {110} > {111} and are higher for surfaces containing oxygen vacancies compared to stoichiometric surfaces, indicating that surface oxidation processes can reduce the stability of surface carbonate groups. Finally, we propose a thermodynamic strategy to predict the evolution of nanoparticle morphology in the presence of CO<sub>2</sub> as the external conditions of temperature and pressure change. We show that there is a thermodynamic driving force dependent on CO<sub>2</sub> adsorption that should be considered when selecting nanoparticle morphologies in catalytic applications.

scholarly journals Surface Stability and Morphology of Calcium Phosphate Tuned by pH Values and Lactic Acid Additives: Theoretical and Experimental Study

2021 ◽  
Author(s):  
Hongwei Chen ◽  
Changchang Lv ◽  
Lin Guo ◽  
Ming Ma ◽  
Xiangfeng Li ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Lactic Acid ◽  
Calcium Phosphate ◽  
Coordination Number ◽  
Density Functional ◽  
Md Simulations ◽  
Ab Initio Molecular Dynamics ◽  
Surface Stability ◽  
Ph Values ◽  
Phosphate Species

The ubiquitous mineralization of calcium phosphate (CaP) facilitates biological organisms to produce hierarchically structured minerals. The coordination number and strength of Ca2+ ions with phosphate species, oxygen-containing additives, and solvent molecules played a crucial role in tuning nucleation processes and surface stability of CaP under the simulated body fluid (SBF) or aqueous solutions upon the addition of oligomeric lactic acid (LACn, n=1, 8) and changing pH values. As revealed by ab initio molecular dynamics (AIMD), density functional theory (DFT), and molecular dynamics (MD) simulations as well as high-throughput experimentation (HTE), the binding of LAC molecules with Ca2+ ions and phosphate species could stabilize both pre-nucleation clusters and brushite (DCPD, CaHPO4·2H2O) surface through intermolecular electrostatic and hydrogen bonding interactions. When the concentration of Ca2+ ions ([Ca2+]) is very low, the amount of the formed precipitation decreased with the addition of LAC based on UV-Vis spectroscopic analysis due to the reduced chance for the LAC capped Ca2+ ions to coordinate with phosphates and the increased solubility in acid solution. With the increasing [Ca2+] concentration, the kinetically stable DCPD precipitation was obtained with high Ca2+ coordination number and low surface energy. Morphologies of DCPD precipitation are in plate, needle, or rod, depending on the initial pH values that tuned by adding NH3·H2O, HCl, or CH3COOH. The prepared samples at pH ≈ 7.4 with different Ca/P ratios exhibited negative zeta potential values, which were correlated with the surface electrostatic potential distributions and potential biological applications.

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