Crystal structure of the high pressure form of Am

Akella, Jagannadham; Johnson, Q.; Thayer, W. J.; Schock, R.N.

doi:10.1016/0022-5088(79)90277-7

Cited by 33 publications

(7 citation statements)

References 9 publications

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“…Application of pressure to the d.h.c.p, form results in a transformation to a face-centered cubic structure. The lattice constant of this form is 4.684 A at 6.5 GPa as reported by Akella, Johnson, Thayer & Schock (1979). In the region of 10-15 GPa a complex pattern of diffraction lines is observed (Roof, Haire, Schiferl, Schwalbe, Kmetko & Smith, 1980) and this form is designated phase III.…”

Section: Introductionmentioning

confidence: 62%

The crystal structure of high-pressure americium, phase III

Roof¹

1981

J Appl Cryst

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Section: Introductionmentioning

confidence: 62%

The crystal structure of high-pressure americium, phase III

Roof¹

1981

J Appl Cryst

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“…[5][6][7][8][9][10] They all agree that AmI and AmII are double hexagonal close-packed ͑dhcp͒ and face-centered cubic ͑fcc͒, respectively, but the transition pressures as well as the structural assignments of AmIII and AmIV have been controversial and confusing. 11 For instance, AmIII was suggested to be monoclinic and AmIV was of the face-centered orthorhombic ͑␣-U͒ type.…”

Section: Introductionmentioning

confidence: 99%

Crystal stability and equation of state for Am: Theory

Söderlind

Landa

2005

Phys. Rev. B

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Density-functional electronic-structure calculations for americium metal concur with the recent reinterpretation of its high-pressure phases ͑AmIII and AmIV͒. The pressure-induced increased dominance of 5f-electron bonding ͑delocalization͒ is well described by electronic-structure calculations when electron spin and orbital correlations are considered. Also the calculated equation of state ͑EOS͒ agrees with experimental findings to a degree typically found for simpler metals. Am is known to adopt low-symmetry crystal structures at 10 GPa ͑AmIII: face-centered orthorhombic͒ and 16 GPa ͑AmIV: primitive orthorhombic͒. These transitions are reproduced by theory with a remarkable accuracy ͑11 and 16 GPa͒. At higher compression ͑60%͒ theory predicts a new bcc phase, AmV, to be stable. We argue that the AmI phase is stabilized by contributions from the d shell to the cohesion whereas all other phases follow from 5f-electron bonding. AmIV has often been associated with the face-centered orthorhombic ␣-U phase, which was its original interpretation. We show that AmIV is in fact closely related to the ␣-Np structure, which is of the same type ͑primitive orthorhombic͒. This distinction is important and explains the believed discord between theory and experiment for AmIV in the past.

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“…In an earlier paper [Akella et al, 1979] we reported extra lines in experiments at and above 11.0 GPa and proposed that these might have resulted from the reaction of Am with the Ni gasket. However, this explanation can now be ruled out,-since a number of runs have been made without any gasketing material or with gold as a gasket material.…”

Section: Resultsmentioning

confidence: 91%

“…Lattice constants are compared in Table 2 Up to 4 GPa we did not observe any structural transformation in Am. We reported earlier that in a run at 6.5 -+ 1.0 GPa, new lines were observed and could be indexed as f½½ with lattice constant of 4.683 _+ 0.018 A [Akella et al, 1979]. On the basis of reading errors of multiple measurements the cell constants are believed to be accurate to _+0.5%.…”

Section: Resultsmentioning

confidence: 91%

Phase transformations in Americium at high pressure: Relation to rare earth elements

Akella¹,

Johnson²,

Schock³

1980

J. Geophys. Res.

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The crystal structure of 243Anl has been investigated up to 18.0 GPa, using a diamond anvil high-pressure apparatus. The normal dhcp form of Am, stable at I atm and room temperature, undergoes threephase transformations below 18.0 GPa. The first transformation occurs at about 5.0 & 1.0 GPa, the second occurs at about 10.0 & 1.0 GPa, and the third occurs at about 15.0 & 1.0 GPa. The structure of the Am phase at 5-GPa pressure is fcc. However, we are unable to determine the structure of the new phases at about 10.0-and 15.0-GPa pressure from our present data. The structural behavior of Am showing that Am undergoes a sequence of structural transformations somewhat similar to the lanthanide metals is discussed.

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Crystal structure of the high pressure form of Am

Cited by 33 publications

References 9 publications

The crystal structure of high-pressure americium, phase III

The crystal structure of high-pressure americium, phase III

Crystal stability and equation of state for Am: Theory

Phase transformations in Americium at high pressure: Relation to rare earth elements

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