First-principles Study of Nitrogen Vacancies in GdN

2011 ◽  
Vol 1290 ◽  
Author(s):  
Atchara Punya ◽  
Tawinan Cheiwchanchamnangij ◽  
Alexander Thiess ◽  
Walter R. L. Lambrecht
Keyword(s):  
First Principles ◽  
Exchange Interactions ◽  
Orbital Method ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
Gadolinium Nitride ◽  
Single Positive ◽  
Positive State ◽  
Neutral Charge State ◽  
Nitrogen Vacancies

ABSTRACTThe electronic structure of nitrogen vacancies in gadolinium nitride are studied using the full-potential linearized muffin-tin orbital method in the local spin density approximation with Hubbard U corrections (LSDA+U). The vacancy is found to have two localized defect levels in the gap, one of each spin. The third electron of each vacancy in the neutral state dopes the conduction band. The single positive state is found to be the ground state for Fermi levels located anywhere within the band gap. The vacancy has a net magnetic moment of 1 μB in the neutral charge state. The presence of the vacancy is found to increase the average exchange interactions between Gd atoms and hence the Curie temperature but only by about a factor 2 compared to GdN without vacancies.

ELASTIC PROPERTIES OF STRAINED FCC AND HCP IRON

1993 ◽  
Vol 07 (01n03) ◽  
pp. 207-211
Author(s):  
T. KRAFT ◽  
M. METHFESSEL ◽  
M. VAN SCHILFGAARDE ◽  
M. SCHEFFLER
Keyword(s):  
Energy Cost ◽  
Interplanar Distance ◽  
Orbital Method ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
Nearest Neighbour ◽  
Density Approximation ◽  
Neighbour Distance ◽  
Large Lattice ◽  
Fcc Phase

Using the full-potential linear muffin-tin orbital method within the local spin-density approximation we analyse the influence of the nearest neighbour distance on fcc(111) or hcp(0001) iron layers. The LDA-LSDA error in describing ferromagnetic phases is determined to be at least 15 mRy/atom. As a consequence of this error, our calculations favour paramagnetic ground states. In this sense, the reported results have some model character. However, our analysis of the elastic energy cost under distortions should hold for transition metals in general. Allowing relaxations of the interplanar distance the fcc phase can become energetically favourable over the hcp phase at large lattice mismatches. The main reason for this behaviour is the enhanced stiffness of the hcp interplanar bonds due to the shortening of the axial c/a ratio.

FIRST-PRINCIPLES HIGH-PRESSURE ELASTIC AND THERMODYNAMIC PROPERTIES OF TANTALUM

2011 ◽  
Vol 25 (10) ◽  
pp. 1393-1407 ◽  
Author(s):  
JING-HE WU ◽  
XIAN-LIN ZHAO ◽  
YOU-LIN SONG ◽  
GUO-DONG WU
Keyword(s):  
Thermodynamic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Equations Of State ◽  
Debye Model ◽  
Thermal Expansivity ◽  
Orbital Method ◽  
Full Potential ◽  
Body Centered Cubic ◽  
Theoretical Results

The all-electron full-potential linearized muffin-tin orbital method, by means of quasi-harmonic Debye model, is applied to investigate the elastic constant and thermodynamic properties of body-centered-cubic tantalum (bcc Ta). The calculated elastic constants of bcc Ta at 0 K is consistent with the previous experimental and theoretical results. Our calculations give the correct trends for the pressure dependence of elastic constants. By using the convenient quasi-harmonic Debye model, we refined the thermal equations of state. The thermal expansivity and some other thermal properties agree well with the previous experimental and theoretical results.

Half-metallic ferromagnetism in V-doped ZnTe semiconductor at reduced dopant concentration

2014 ◽  
Vol 28 (13) ◽  
pp. 1450104 ◽  
Author(s):  
M. Sajjad ◽  
H. X. Zhang ◽  
N. A. Noor ◽  
S. M. Alay-e-Abbas ◽  
M. Abid ◽  
...  
Keyword(s):  
Density Functional ◽  
Spin Exchange ◽  
Density Functional Theory Calculations ◽  
Orbital Method ◽  
Ferromagnetic Behavior ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
Generalized Gradient ◽  
Half Metallic ◽  
Bonding Properties

In this study, we examine the structural, electronic, magnetic and bonding properties of zincblende phase Zn 1-x V x Te (x = 0.0625, 0.125, 0.25) compounds to present them as suitable candidates for spintronic applications. Density functional theory calculations have been used by implementing the accurate full-potential linear-augmented-planewave plus local-orbital method. Structural properties have been computed using Wu–Cohen generalized gradient approximation, whereas the modified Becke and Johnson local (spin) density approximation (mBJLDA) function has been employed for the evaluating ground state electronic properties and ferromagnetic behavior. The half-metallic (HM) ferromagnetism in Zn 1-x V x Te is analyzed in terms of V -3d states and it is shown that mBJLDA predicts wide HM gaps which promise the possibility of achieving V -doped ZnTe with high Curie temperature. The spin exchange splittings Δx(d) and Δx(pd) have been estimated and the contribution of conduction band (CB) and valence band (VB) in exchange splitting is calculated in terms of the exchange constants N0α and N0β. Furthermore, spin-polarized charge density calculation is presented for elucidating the bonding nature, while pressure dependence of total magnetic moment for three concentrations of V -doped ZnTe is also discussed.

scholarly journals A First-Principles Study of the Phase Stability of FCC-Based Ti-Al Alloys

1992 ◽  
Vol 278 ◽  
Author(s):  
Mark Asta ◽  
Didier De Fontaine ◽  
Mark Van Schilfgaarde ◽  
Marcel Sluiter ◽  
Michael Methfessel
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Cluster Variation Method ◽  
Stability Study ◽  
Al Alloys ◽  
Variation Method ◽  
Orbital Method ◽  
Temperature Phase ◽  
Full Potential ◽  
Cluster Variation

AbstractIn this paper we present results of a first-principles phase stability study of fcc-based Ti-Al alloys. In particular, the full-potential linear muffin tin orbital method has been used to determine heats of formation and other zero-temperature properties of 9 fcc ordered superstructures as well as fcc and hcp Ti, and fcc Al. From these results a set of effective cluster interactions are determined which are used in a cluster variation method calculation of the thermodynamic properties and the composition-temperature phase diagram of fcc-based alloys.

First-principles study of phase stability of Ti–Al intermetallic compounds

1993 ◽  
Vol 8 (10) ◽  
pp. 2554-2568 ◽  
Author(s):  
Mark Asta ◽  
Didier de Fontaine ◽  
Mark van Schilfgaarde
Keyword(s):  
Intermetallic Compounds ◽  
Phase Stability ◽  
First Principles ◽  
Experimental Studies ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Orbital Method ◽  
Temperature Phase ◽  
Full Potential ◽  
Cluster Variation

Thermodynamic and structural properties of fcc- and hcp-based Ti–Al alloys are calculated from first-principles and are used to perform an ab initio study of phase stability for the intermetallic compounds in this system. The full potential linear muffin tin orbital method is used to determine heats of formation and other zero-temperature properties of 9 fcc- and 7 hcp-based intermetallic compounds, as well as of elemental fcc and hcp Ti and Al. From the results of these calculations, sets of effective cluster interactions are derived and are used in a cluster variation method calculation of the solid-state portion of the composition-temperature phase diagram for fcc- and hcp-based alloy phases. The results of our calculations are compared with those of experimental studies of stable and metastable phases in the Ti–Al system.

Half-Metallic Ferromagnetism in MgS by Doping with Sp-Element: A First-Principles Calculations

2013 ◽  
Vol 665 ◽  
pp. 22-28 ◽  
Author(s):  
Moovendran Yogeswari ◽  
Rajagopalan Umamaheswari ◽  
G. Kalpana
Keyword(s):  
First Principles ◽  
Partial Density ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Half Metallic ◽  
Exchange Correlation ◽  
Metallic Ferromagnetism ◽  
Half Metallic Ferromagnetism

The first-principles calculations using full potential linearized augmented plane wave method (FP-LAPW) was performed to determine the influence of dopants (N, P, As and Sb) on the electronic structure of MgS in the rock salt structure. In the present work both local spin density approximation (LSDA) and generalized gradient approximation (GGA) were used for exchange correlation potential functional. Among the group V elements N-doping alone induce half-metallic ferromagnetism in MgS host with a magnetic moment of 1.00 μB/f.u. Total energy calculations show that ferromagnetic state is more stable than non-magnetic state in all the compounds. The ground state properties such as equilibrium lattice constant, bulk modulus and bond length were calculated. The spin polarized electronic band structure, total and partial density of states calculations were carried out to study the origin of half-metallic ferromagnetism in these compounds. The difference between two exchange-correlation functions is also analyzed.

Elastic Constants and Related Properties of the Group III-Nitrides

1995 ◽  
Vol 395 ◽  
Author(s):  
Kwiseon Kim ◽  
Walter R. L. Lambrecht ◽  
B. Segall
Keyword(s):  
Elastic Constants ◽  
First Principles ◽  
Bond Angle ◽  
Local Density ◽  
Group Iii Nitrides ◽  
Internal Displacement ◽  
Orbital Method ◽  
Model Parameters ◽  
Full Potential ◽  
Group Iii

ABSTRACTThe elastic constants of the Group-III nitrides, c-BN, AlN and GaN were calculated from first-principles using the full-potential linear muffin-tin orbital method and local density approximation. The relation between the elatic constants in zincblende and wurtzite is studied by means of a tensor coordinate transformation approach. The latter combined with a correction for the internal displacement of the rotated tetrahedra is found to provide good results for the Ch11Ch12 and Ch44 but not for Ch13 and Ch33. These two require explicit calculations involving distortions along the c-axis. The calculations also provide information on the transverse optical phonons. By deriving Keating model parameters we show that BN is much stiffer against bond-angle distortions than the other nitrides.

AB INITIO CALCULATION OF MAGNETIC MOMENTS, HYPERFINE FIELDS, MAGNETIC ANISOTROPY AND EXCHANGE INTERACTIONS IN RARE-EARTH INTERMETALLICS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 710-715 ◽  
Author(s):  
K. HUMMLER ◽  
M. LIEBS ◽  
T. BEUERLE ◽  
M. FÄHNLE
Keyword(s):  
Rare Earth ◽  
Magnetic Anisotropy ◽  
Exchange Coupling ◽  
Magnetic Moments ◽  
Exchange Interactions ◽  
Orbital Method ◽  
Local Spin Density Approximation ◽  
Hyperfine Fields ◽  
Atomic Sphere ◽  
Sphere Approximation

The intrinsic magnetic properties of R2Fe14B (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb) are calculated from first principles within the local-spin-density approximation and the linear-muffin-tin-orbital method in atomic-sphere approximation. The total magnetization is in excellent agreement with experimental data. The local magnetic moments of the crystallographically inequivalent Fe sites appear to be not proportional to the local hyperfine fields. It is shown that the rare-earth contribution to the magnetic anisotropy may be qualitatively related to the electrostatic interaction of the aspherical 4f charge density with the crystal field. The effective intersublattice exchange coupling is evaluated from the change of the total energy upon 4f spin reversion.

First-Principles Calculation of the Orbital Magnetic Moment of O and Cr in Half-metallic CrO2

2002 ◽  
Vol 718 ◽  
Author(s):  
Horng-Tay Jeng ◽  
G. Y. Guo
Keyword(s):  
Magnetic Moment ◽  
Magnetic Circular Dichroism ◽  
First Principles Calculation ◽  
Orbital Method ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
Orbital Moment ◽  
Half Metallic ◽  
Orbital Magnetic Moment ◽  
Good Agreement

AbstractThe electronic and magnetic properties of half-metallic CrO2 have been studied by using the full-potential linearized muffin-tin orbital method within the local spin-density approximation (LSDA)+U approach. It is found that the orbital magnetic moment of Cr atom is quenched while O atom exhibit relatively significant orbital moment in CrO2. For the Hubbard U of 3 eV, LSDA+U gives the orbital moment of -0.051μB/atom for Cr and -0.0025μB/atom for O, being in good agreement with the experimental orbital moments of -0.05 for Cr and -0.003μB/atom for O, respectively. In contrast, LSDA gives the orbital moment of -0.037 for Cr and -0.0011 μB/atom for O, being too small as compared with the magnetic circular dichroism measurements. For the larger U considered in this work, both spin and orbital moments almost increase linearly with respect to U.

Site Dependence of Electronic Structure of Gd Impurities in GaN

2011 ◽  
Vol 1290 ◽  
Author(s):  
Tawinan Cheiwchanchamnangij ◽  
Atchara Punya ◽  
Walter R. L. Lambrecht
Keyword(s):  
Electronic Structure ◽  
Magnetic Moments ◽  
Interstitial Site ◽  
Nitrogen Vacancy ◽  
Orbital Method ◽  
Full Potential ◽  
Local Spin Density Approximation ◽  
Site Dependence ◽  
Structure Calculations ◽  
Energy Of Formation

ABSTRACTElectronic structure calculations are reported for Gd in GaN on Ga as well as on N site and for pairs of Gd on neighboring Ga and N sites, using the full-potential linearized muffin-tin orbital method in the local spin density approximation with Hubbard U corrections (LSDA+U). The energy of formation for the N site is found to be much higher than for the Ga site even after relaxations are included. The GdN configuration is found to be at best metastable (in ZB). In WZ and in the pair configurations, the Gd is found to move toward an interstitial site leaving a nitrogen vacancy behind. The electronic structure of these structures and their magnetic moments are discussed.

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