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Ab initio investigation of monoclinic phase stability and martensitic transformation in crystalline polyethylene

Olsson, Pär LU ; Hyldgaard, Per ; Schröder, Elsebeth ; Persson Jutemar, Elin ; Andreasson, Eskil and Kroon, Martin (2018) In Physical Review Materials 2(7).
Abstract
We study the phase stability and martensitic transformation of orthorhombic and monoclinic polyethylene by means of density functional theory using the nonempirical consistent-exchange vdW-DF-cx functional [Phys. Rev. B 89, 035412 (2014)]. The results show that the orthorhombic phase is the most stable of the two. Owing to the occurrence of soft librational phonon modes, the monoclinic phase is predicted not to be stable at zero pressure and temperature, but becomes stable when subjected to compressive transverse deformations that pin the chains and prevent them from wiggling freely. This theoretical characterization, or prediction, is consistent with the fact that the monoclinic phase is only observed experimentally when the material is... (More)
We study the phase stability and martensitic transformation of orthorhombic and monoclinic polyethylene by means of density functional theory using the nonempirical consistent-exchange vdW-DF-cx functional [Phys. Rev. B 89, 035412 (2014)]. The results show that the orthorhombic phase is the most stable of the two. Owing to the occurrence of soft librational phonon modes, the monoclinic phase is predicted not to be stable at zero pressure and temperature, but becomes stable when subjected to compressive transverse deformations that pin the chains and prevent them from wiggling freely. This theoretical characterization, or prediction, is consistent with the fact that the monoclinic phase is only observed experimentally when the material is subjected to mechanical loading. Also, the estimated threshold energy for the combination of lattice deformation associated with the T1 and T2 transformation paths (between the orthorhombic and monoclinic phases) and chain shuffling is found to be sufficiently low for thermally activated back transformations to occur. Thus, our prediction is that the crystalline part can transform back from the monoclinic to the orthorhombic phase upon unloading and/or annealing, which is consistent with experimental observations. Finally, we observe how a combination of such phase transformations can lead to a fold-plane reorientation from {110} to {100} type in a single orthorhombic crystal. (Less)
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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Yielding, Martensitic phase transformations, Polyethylene
in
Physical Review Materials
volume
2
issue
7
article number
075602
pages
13 pages
publisher
American Physical Society
external identifiers
  • scopus:85051639191
ISSN
2475-9953
language
English
LU publication?
yes
id
014d68dd-4c33-4823-a1aa-561e1ae148d1
alternative location
https://journals-aps-org.ludwig.lub.lu.se/prmaterials/abstract/10.1103/PhysRevMaterials.2.075602
date added to LUP
2018-07-10 20:30:52
date last changed
2021-10-06 03:32:23
@article{014d68dd-4c33-4823-a1aa-561e1ae148d1,
  abstract     = {We study the phase stability and martensitic transformation of orthorhombic and monoclinic polyethylene by means of density functional theory using the nonempirical consistent-exchange vdW-DF-cx functional [Phys. Rev. B 89, 035412 (2014)]. The results show that the orthorhombic phase is the most stable of the two. Owing to the occurrence of soft librational phonon modes, the monoclinic phase is predicted not to be stable at zero pressure and temperature, but becomes stable when subjected to compressive transverse deformations that pin the chains and prevent them from wiggling freely. This theoretical characterization, or prediction, is consistent with the fact that the monoclinic phase is only observed experimentally when the material is subjected to mechanical loading. Also, the estimated threshold energy for the combination of lattice deformation associated with the T1 and T2 transformation paths (between the orthorhombic and monoclinic phases) and chain shuffling is found to be sufficiently low for thermally activated back transformations to occur. Thus, our prediction is that the crystalline part can transform back from the monoclinic to the orthorhombic phase upon unloading and/or annealing, which is consistent with experimental observations. Finally, we observe how a combination of such phase transformations can lead to a fold-plane reorientation from {110} to {100} type in a single orthorhombic crystal.},
  author       = {Olsson, Pär and Hyldgaard, Per and Schröder, Elsebeth and Persson Jutemar, Elin and Andreasson, Eskil and Kroon, Martin},
  issn         = {2475-9953},
  language     = {eng},
  month        = {07},
  number       = {7},
  publisher    = {American Physical Society},
  series       = {Physical Review Materials},
  title        = {Ab initio investigation of monoclinic phase stability and martensitic transformation in crystalline polyethylene},
  url          = {https://journals-aps-org.ludwig.lub.lu.se/prmaterials/abstract/10.1103/PhysRevMaterials.2.075602},
  volume       = {2},
  year         = {2018},
}