The subtlety of resolving orbital angular momenta in calculating Hubbard U parameters in the density functional tight-binding theory and its delicacy is illustrated by the calculated magnetic properties of carbon clusters

2018 ◽  
Vol 137 (10) ◽  
Author(s):  
T. W. Yen ◽  
S. K. Lai
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Tight Binding ◽  
Carbon Clusters ◽  
Binding Theory ◽  
Angular Momenta ◽  
Hubbard U

Electronic and Magnetic Properties of Half Metallic Heusler Alloy Co2mnsi: A First-Principles Study

2017 ◽  
pp. 31-36
Author(s):  
Prakash Sharma ◽  
Gopi Chandra Kaphle
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moment ◽  
Heusler Alloy ◽  
Density Functional ◽  
Heusler Alloys ◽  
Tight Binding ◽  
Lattice Parameter ◽  
Half Metallic ◽  
Electronic And Magnetic Properties ◽  
Sphere Approximation

Heusler alloys have been of great interest because of their application in the field of modern technological word. Electronic and magnetic properties of Co, Mn, Si and the Heusler alloy Co2MnSi have been studied using Density functional theory based Tight Binding Linear Muffin Tin Orbital with Atomic Sphere Approximation (TB-LMTO-ASA) approach. From the calculation lattice parameter of optimized structure of Co, Mn, Si and Co2MnSi are found to be 2.52A0 , 3.49A0 , 5.50A0 , 5.53A0 respectively. Band structure calculations show that Co and Mn are metallic, Si as semi-conducting while the Heusler alloy Co2MnSi as half-metallic in nature with band gap 0.29eV. The charge density plot indicates major bonds in Co2MnSi are ionic in nature. Magnetic property has been studied using the density of states (DOS), indicating that Co and Co2MnSi are magnetic with magnetic moment 2.85μB and 4.91μB respectively. The contribution of orbitals in band, DOS and magnetic moment are due to d-orbitals of Co and Mn and little from s and p-orbital of Si in Co2MnSi.The Himalayan Physics Vol. 6 & 7, April 2017 (31-36)

A SELF-CONSISTENT-CHARGE DENSITY-FUNCTIONAL TIGHT-BINDING THEORY BASED MOLECULAR DYNAMICS SIMULATION OF A ZWITTERIONIC GLYCINE IN AN EXPLICIT WATER ENVIRONMENT

2013 ◽  
Vol 12 (04) ◽  
pp. 1350019 ◽  
Author(s):  
Y. ZHAI ◽  
Y. L. ZHAO
Keyword(s):  
Molecular Dynamics ◽  
Amino Acids ◽  
Charge Density ◽  
Density Functional ◽  
Water Environment ◽  
Tight Binding ◽  
Water Molecules ◽  
Binding Theory ◽  
Self Consistent ◽  
The Impact

A zwitterionic glycine (zGLY) is adopted as an example to study the impact of water environment (310 H2O molecules) on the molecular structure and energetics using a self-consistent-charge density-functional tight-binding theory based molecular dynamics (SCC-DFTB/MD) method. It is found that maximal eight hydrogen bonds could be formed simultaneously between eight water molecules and the zGLY. The ability of the COO- terminal to adsorb water molecules is stronger than the [Formula: see text] terminal with respect to hydrogen bonding with more water molecules and exhibits lower adiabatic adsorption energies. The zGLY's intramolecular hydrogen bond appeared unpredictably, without involving any proton transfer and generally helpful for enhancing the system stability. Water molecules play an important role to stabilize the zwitterionic amino acids and restrain the proton migration from the [Formula: see text] to the COO− group. Our results show that the SCC-DFTB/MD method could successfully describe geometry dynamical evolutions and energetics of biomolecules in a nanoscale simulation with the presence of a large number of water molecules. Our study not only verified the feasibility of a QM level methodology for describing the aqueous states of biochemical molecules, but also gave a clear evidence for the impact of water environment on amino acids.

scholarly journals Density-Functional and Tight-Binding Theory of Silicene and Silicane

2018 ◽  
pp. 23-41
Author(s):  
V. Zólyomi ◽  
N. D. Drummond ◽  
J. R. Wallbank ◽  
V. I. Fal’ko
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
Binding Theory

scholarly journals First-principles study of structural, electronic and magnetic properties of Co-based quaternary Heusler compounds: CoFeCrAl, CoFeTiAs, CoFeCrGa and CoMnVAs

BIBECHANA ◽  
2017 ◽  
Vol 15 ◽  
pp. 50-59 ◽  
Author(s):  
Bikram Pandey ◽  
Ram Babu Ray ◽  
Gopi Chandra Kaphle
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Tight Binding ◽  
Lattice Parameter ◽  
Total Density ◽  
Heusler Compounds ◽  
Electronic Band ◽  
Half Metallic ◽  
Electronic And Magnetic Properties

We study the Structural, Electronic and Magnetic properties of Co-based LiMgPdSn-types of quaternary Heusler compounds (CoFeCrAl, CoFeTiAs, CoFeCrGa, and CoMnVAS) using Density Functional Theory (DFT) implemented on Tight Binding Linear Muffin-Tin Orbital within Atomic Sphere Approximation(TB-LMTO-ASA) Code. The optimized value of lattice parameter for CoFeCrAl, CoFeTiAs, CoFeCrGa and CoMnVAs are found to be 5.61A˚, 5.76 A˚, 5.61A˚ and 5.71A˚ respectively. From the calculation of electronic band structure and spin polarized total density of states (DOS), we found that CoFeCrAl and CoFeCrGa are spin-gapless semiconductor with half-metallic gap of 0.82eV and 0.25eV respectively. CoFeTiAs half-metals (Nearly spin-gapless semiconductor) with half-metallic gap 0.38 eV and CoMnVAs is found to be nearly gapless half-metal. Magnetic moment of these compounds almost obey the Slater-Pauling rules. All these compounds  expected to have high curie temperature which makes them significant for spintroincs/magnetoelectroincs applications.BIBECHANA 15 (2018) 50-59 

scholarly journals An ab initio study of the magnetic properties of strontium hexaferrite

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
C. Tejera-Centeno ◽  
S. Gallego ◽  
J. I. Cerdá
Keyword(s):  
Magnetic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Strontium Hexaferrite ◽  
Multiscale Approach ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Hubbard U ◽  
Exchange Constants ◽  
O 19

AbstractThe magnetic properties of $${\text{SrFe}}_{12}{\text{O}}_{19}$$ SrFe 12 O 19 , a paradigmatic hexaferrite for permanent magnet applications, have been addressed in detail combining density functional theory including spin–orbit coupling and a Hubbard U term with Monte Carlo simulations. This multiscale approach allows to estimate the Néel temperature of the material from ab initio exchange constants, and to determine the influence of different computational conditions on the magnetic properties by direct comparison versus available experimental data. It is found that the dominant influence arises from the choice of the Hubbard U term, with a value in the 2–3 eV range as the most adequate to quantitatively reproduce the two most relevant magnetic properties of this material, namely: its large perpendicular magnetocrystalline anisotropy and its elevated Néel temperature.

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