Total energies and bonding for crystallographic structures in titanium-carbon and tungsten-carbon systems

Price, David L.; Cooper, Bernard R.

doi:10.1103/physrevb.39.4945

Cited by 359 publications

(107 citation statements)

References 29 publications

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“…This tendency of DOS combined with variation in N͑E F ͒ indicates that nitrogen vacancies stabilize NaCl phase over the WC phase. 44,45 Hugosson et al 45 have studied the phase stability and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide. This study shows that carbon vacancies lower the energy of NaCl phase and makes the phase more stable.…”

Section: B Cluster Expansion and Phase Stabilitymentioning

confidence: 99%

Cluster expansion Monte Carlo study of phase stability of vanadium nitrides

et al. 2010

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Phase stability of stable and metastable vanadium nitrides is studied using density functional theory ͑DFT͒ based total-energy calculations combined with cluster expansion Monte Carlo simulation and supercell methods. We have computed the formation enthalpy of the various stable and metastable vanadium nitride phases considering the available structural models and found that the formation enthalpies of the different phases decrease in the same order as they appear in the experimental aging sequence. DFT calculations are known to show stoichiometric V 2 N to be polymorphic in ⑀-Fe 2 N and -Fe 2 N structures within a few meV and VN to be more stable in WC͑B h ͒ phase than in the experimentally observed NaCl͑B1͒ structure. As these nitrides are known to be generally nonstoichiometric due to presence of nitrogen vacancies, we used cluster expansion and supercell methods for examining the effect of nitrogen vacancies on the phase stability. It is found that nitrogen vacancies, represented by ᮀ, stabilize ⑀-Fe 2 N phase of V 2 N 1−x ᮀ x and NaCl͑B1͒ phase of VN 1−x ᮀ x compared to -Fe 2 N and WC͑B h ͒ phases respectively, rendering the computed phase stability scenario to be in agreement with experiments. Analysis of supercell calculated electronic density of states ͑DOS͒ of VN 1−x ᮀ x with varying x, shows that the nitrogen vacancies increase the DOS at Fermi level in WC phase, whereas they decrease the DOS in NaCl phase. And this serves as the mechanism of enhancement of the stability of the NaCl phase. Monte Carlo simulations were used for computing the finite temperature formation enthalpies of these phases as a function of nitrogen-vacancy concentration and found close agreement for NaCl͑B1͒ phase of VN 1−x ᮀ x for which measured values are available.

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Section: B Cluster Expansion and Phase Stabilitymentioning

confidence: 99%

Cluster expansion Monte Carlo study of phase stability of vanadium nitrides

et al. 2010

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“…In order to study the electronic structure of Cf, we have used the full-potential linear muffin-tin-orbital (FPLMTO) method 23,24 . The calculations were based on the generalised gradient approximation and we used the Perdew and Wang parameterisation for the exchange and correlation potential.…”

Section: Theorymentioning

confidence: 99%

Structural investigation of californium under pressure

et al. 2013

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The high pressure structural behaviour of californium has been studied experimentally and theoretically up to 100 GPa. A valence change from divalent to trivalent forms was observed under modest pressure revealing californium to be the only actinide to exhibit more than one metallic valence at near to ambient conditions as is the case for cerium in the lanthanide series. 3 metallic valencies and 4 different crystallographic phases were observed in californium as a function of pressure. High-pressure techniques, synchrotron radiation and ab initio electronic structure calculations of total energies were used to investigate the material and to determine the role which californiums 5f electrons play in influencing these transitions.The crystallographic structures observed are similar to those found in the preceding actinide elements, curium and americium with the initially localized 5f states becoming completely delocalized under the influence of high pressure.

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“…7 Explicit orbital polarization can be taken into account self-consistently by means of an eigenvalue shift, ⌬V m ϭϪE 3 L z m l , at each atom site. 6 Here, L z is the z component of the total orbital moment of the atom, m l is the magnetic quantum number, and E 3 is the Racah parameter which is self-consistently evaluated at each iteration.…”

Section: Methodsmentioning

confidence: 99%

Ab initio study of anisotropic magnetism in uranium compounds

Collins

Kioussis

Lim

et al. 1999

Journal of Applied Physics

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Articles you may be interested inRelevance of 4f-3d exchange to finite-temperature magnetism of rare-earth permanent magnets: An ab-initiobased spin model approach for NdFe12N J. Appl. Phys. 119, 213901 (2016) We have applied two methods to investigate the origin in the electronic structure of the unusual magnetic behavior of the uranium monochalcogenides and monopnictides. First, we have carried out spin-polarized electronic structure calculations based on the full-potential linearized muffin-tin orbital ͑FPLMTO͒ method with only spin-polarization ͑orbital polarization only via spin-orbit coupling͒ and also with orbital polarization correction. Second, we have carried out first-principles calculations synthesizing ͑1͒ a phenomenological theory of orbitally driven magnetism using a model Hamiltonian which incorporates explicitly the hybridization-induced and Coulomb exchange interactions on an equal footing, and ͑2͒ FPLMTO electronic structure calculations allowing a first-principles evaluation of the parameters entering the model Hamiltonian. Within the purely band calculation greater success is obtained for the zero-temperature ordered moments for the more itinerant compounds ͑US and UP͒, while the synthesis of phenomenology and electronic structure method gives better agreement with experiment for the more localized pnictides ͑UBi, USb͒. Results for the ordered moments and ordering temperatures are presented, and the validity and limitations of the two methods are discussed.

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Total energies and bonding for crystallographic structures in titanium-carbon and tungsten-carbon systems

Cited by 359 publications

References 29 publications

Cluster expansion Monte Carlo study of phase stability of vanadium nitrides

Cluster expansion Monte Carlo study of phase stability of vanadium nitrides

Structural investigation of californium under pressure

Ab initio study of anisotropic magnetism in uranium compounds

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