The 5f localization/delocalization in
square and hexagonal americium monolayers: a FP-LAPW electronic structure
study |
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Authors: | D Gao A K Ray |
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Institution: | (1) Physics Department, P.O. Box 19059, University of Texas at Arlington, Arlington, Texas 76019, USA |
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Abstract: | The electronic and geometrical properties of bulk americium and square and
hexagonal americium monolayers have been studied with the full-potential
linearized augmented plane wave (FP-LAPW) method. The effects of several
common approximations are examined: (1) non-spin polarization (NSP) vs. spin
polarization (SP); (2) scalar-relativity (no spin-orbit coupling (NSO)) vs.
full-relativity (i.e., with spin-orbit (SO) coupling included); (3)
local-density approximation (LDA) vs. generalized-gradient approximation
(GGA). Our results indicate that both spin polarization and spin orbit
coupling play important roles in determining the geometrical and electronic
properties of americium bulk and monolayers. A compression of both americium
square and hexagonal monolayers compared to the americium bulk is also
observed. In general, the LDA is found to underestimate the equilibrium
lattice constant and give a larger total energy compared to the GGA
calculations. While spin orbit coupling shows a similar effect on both
square and hexagonal monolayer calculations regardless of the model, GGA
versus LDA, an unusual spin polarization effect on both square and hexagonal
monolayers is found in the LDA results as compared with the GGA results. The
5f delocalization transition of americium is employed to explain our observed
unusual spin polarization effect. In addition, our results at the LDA level
of theory indicate a possible 5f delocalization could happen in the americium
surface within the same Am II (fcc crystal structure) phase, unlike the
usually reported americium 5f delocalization which is associated with crystal
structure change. The similarities and dissimilarities between the
properties of an Am monolayer and a Pu monolayer are discussed in detail. |
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Keywords: | 71 15 -m Methods of electronic structure calculations 71 27+a Strongly correlated electron systems heavy fermions 73 20 At Surface states band structure electron density of states 75 50 Ee Antiferromagnetics |
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