Magnetic Phase Diagram of Transition Metal Doped ZnO from Density Functional Theory Calculations and Monte Carlo Simulations

2010 ◽  
Vol 1260 ◽  
Author(s):  
Sanjeev K. Nayak ◽  
Heike C. Herper ◽  
Peter Entel
Keyword(s):  
Monte Carlo ◽  
Curie Temperature ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Density Functional ◽  
Magnetic Phase Diagram ◽  
Density Functional Theory Calculations ◽  
Antiferromagnetic Coupling ◽  
Doped Zno ◽  
Co Concentrations

AbstractTransition metals doped ZnO are possible candidates for multiferroics. Here, we have investigated the evolution of ferromagnetism due to Co dopants. The magnetic properties have been studied for Co concentrations from 0 to 100% by using ab-initio methods, i.e., KKR Green's function techniques. In order to estimate the Curie temperature we have performed Monte Carlo simulations with ab-initio calculated exchange parameters.From our calculations the onset of ferromagnetism occurs between 5 to 20% of Co depending on the numerical details of KKR method used. For Co concentrations larger than 50% the system is dominated by antiferromagnetic coupling and no Curie temperature can be obtained.

scholarly journals Configurational Entropy in Multicomponent Alloys: Matrix Formulation from Ab Initio Based Hamiltonian and Application to the FCC Cr-Fe-Mn-Ni System

Entropy ◽  
2019 ◽  
Vol 21 (1) ◽  
pp. 68 ◽  
Author(s):  
Antonio Fernández-Caballero ◽  
Mark Fedorov ◽  
Jan Wróbel ◽  
Paul Mummery ◽  
Duc Nguyen-Manh
Keyword(s):  
Solid Solution ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Density Functional ◽  
Elevated Temperatures ◽  
Thermodynamic Integration ◽  
Matrix Formulation ◽  
Configuration Entropy ◽  
Multi Body

Configuration entropy is believed to stabilize disordered solid solution phases in multicomponent systems at elevated temperatures over intermetallic compounds by lowering the Gibbs free energy. Traditionally, the increment of configuration entropy with temperature was computed by time-consuming thermodynamic integration methods. In this work, a new formalism based on a hybrid combination of the Cluster Expansion (CE) Hamiltonian and Monte Carlo simulations is developed to predict the configuration entropy as a function of temperature from multi-body cluster probability in a multi-component system with arbitrary average composition. The multi-body probabilities are worked out by explicit inversion and direct product of a matrix formulation within orthonomal sets of point functions in the clusters obtained from symmetry independent correlation functions. The matrix quantities are determined from semi canonical Monte Carlo simulations with Effective Cluster Interactions (ECIs) derived from Density Functional Theory (DFT) calculations. The formalism is applied to analyze the 4-body cluster probabilities for the quaternary system Cr-Fe-Mn-Ni as a function of temperature and alloy concentration. It is shown that, for two specific compositions (Cr 25Fe 25Mn 25Ni 25 and Cr 18Fe 27Mn 27Ni 28), the high value of probabilities for Cr-Fe-Fe-Fe and Mn-Mn-Ni-Ni are strongly correlated with the presence of the ordered phases L1 2 -CrFe 3 and L1 0-MnNi, respectively. These results are in an excellent agreement with predictions of these ground state structures by ab initio calculations. The general formalism is used to investigate the configuration entropy as a function of temperature and for 285 different alloy compositions. It is found that our matrix formulation of cluster probabilities provides an efficient tool to compute configuration entropy in multi-component alloys in a comparison with the result obtained by the thermodynamic integration method. At high temperatures, it is shown that many-body cluster correlations still play an important role in understanding the configuration entropy before reaching the solid solution limit of high-entroy alloys (HEAs).

Influence of Hydrogen Bonding on the Structure of the (001) Corundum–Water Interface. Density Functional Theory Calculations and Monte Carlo Simulations

Langmuir ◽  
2014 ◽  
Vol 30 (10) ◽  
pp. 2722-2728 ◽  
Author(s):  
Jiří Janeček ◽  
Roland R. Netz ◽  
Mathias Flörsheimer ◽  
Reinhardt Klenze ◽  
Bernd Schimmelpfennig ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Hydrogen Bonding ◽  
Monte Carlo Simulations ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Water Interface ◽  
Functional Theory

Ab Initio Calculation of Mechanical Properties of Stacking Fault in 3C-SiC: Effect of Stress and Doping

2012 ◽  
Vol 717-720 ◽  
pp. 415-418
Author(s):  
Yoshitaka Umeno ◽  
Kuniaki Yagi ◽  
Hiroyuki Nagasawa
Keyword(s):  
Mechanical Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Stacking Faults ◽  
Single Layer ◽  
Local Strain ◽  
Density Functional Theory Calculations ◽  
Stacking Fault ◽  
Functional Theory ◽  
N Doping

We carry out ab initio density functional theory calculations to investigate the fundamental mechanical properties of stacking faults in 3C-SiC, including the effect of stress and doping atoms (substitution of C by N or Si). Stress induced by stacking fault (SF) formation is quantitatively evaluated. Extrinsic SFs containing double and triple SiC layers are found to be slightly more stable than the single-layer extrinsic SF, supporting experimental observation. Effect of tensile or compressive stress on SF energies is found to be marginal. Neglecting the effect of local strain induced by doping, N doping around an SF obviously increase the SF formation energy, while SFs seem to be easily formed in Si-rich SiC.

Constructing accurate interaction potentials to describe the microsolvation of protonated methane by helium atoms

2017 ◽  
Vol 19 (12) ◽  
pp. 8307-8321 ◽  
Author(s):  
Dennis Kuchenbecker ◽  
Felix Uhl ◽  
Harald Forbert ◽  
Georg Jansen ◽  
Dominik Marx
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Path Integral ◽  
Interaction Potential ◽  
Stationary Point ◽  
Path Integral Monte Carlo ◽  
Interaction Potentials ◽  
Helium Atoms

An ab initio-derived interaction potential is derived and used in path integral Monte Carlo simulations to investigate stationary-point structures of CH5+ microsolvated by up to four helium atoms.

Carrier induced ferromagnetism in Mn-doped ZnO: Monte Carlo simulations

2008 ◽  
Vol 92 (15) ◽  
pp. 152511 ◽  
Author(s):  
T. M. Souza ◽  
I. C. da Cunha Lima ◽  
M. A. Boselli
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Doped Zno ◽  
Mn Doped

scholarly journals Solvent Effect on the Structure and Properties of RGD Peptide (1FUV) at Body Temperature (310 K) Using Ab Initio Molecular Dynamics

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3434
Author(s):  
Khagendra Baral ◽  
Puja Adhikari ◽  
Bahaa Jawad ◽  
Rudolf Podgornik ◽  
Wai-Yim Ching
Keyword(s):  
Molecular Dynamics ◽  
Body Temperature ◽  
Ab Initio ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Rgd Peptide ◽  
Ab Initio Molecular Dynamics ◽  
Quantum Mechanical ◽  
Aqueous Environment ◽  
Structure And Properties

The structure and properties of the arginine-glycine-aspartate (RGD) sequence of the 1FUV peptide at 0 K and body temperature (310 K) are systematically investigated in a dry and aqueous environment using more accurate ab initio molecular dynamics and density functional theory calculations. The fundamental properties, such as electronic structure, interatomic bonding, partial charge distribution, and dielectric response function at 0 and 310 K are analyzed, comparing them in dry and solvated models. These accurate microscopic parameters determined from highly reliable quantum mechanical calculations are useful to define the range and strength of complex molecular interactions occurring between the RGD peptide and the integrin receptor. The in-depth bonding picture analyzed using a novel quantum mechanical metric, the total bond order (TBO), quantifies the role played by hydrogen bonds in the internal cohesion of the simulated structures. The TBO at 310 K decreases in the dry model but increases in the solvated model. These differences are small but extremely important in the context of conditions prevalent in the human body and relevant for health issues. Our results provide a new level of understanding of the structure and properties of the 1FUV peptide and help in advancing the study of RGD containing other peptides.

scholarly journals Two-dimensional Dirac fermions on oxidized black phosphorus

2019 ◽  
Vol 21 (43) ◽  
pp. 24206-24211
Author(s):  
Seoung-Hun Kang ◽  
Jejune Park ◽  
Sungjong Woo ◽  
Young-Kyun Kwon
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Black Phosphorus ◽  
Inversion Symmetry ◽  
Dirac Fermions ◽  
Two Dimensional ◽  
Functional Theory

Using ab initio density functional theory calculations, we find four-fold degenerate Dirac points protected by two nonsymmorphic symmetries in phosphorene oxide with the inversion symmetry broken.

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