Density-functional description of polymer crystals: A comparative study of recent van der Waals functionals

Pham, Thinh; Ramprasad, Rampi; Nguyen, Huy-Viet

doi:10.1063/1.4953170

Cited by 15 publications

(12 citation statements)

References 43 publications

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“…Density functional theory (DFT) has proved successful at accurately describing the electronic structure [238], crystalline structure and mechanical properties of crystalline PE [239]. DFT calculations on PE unit cell parameters lead to a = 6.7 -6.8 Å and b = 4.5 -4.6 Å [240], much lower than those obtained in the experiments for bulk semicrystalline PE and single crystals [122,[241][242][243][244] likely due to overestimated intermolecular bond strengths.…”

Section: The Orthorhombic Unit Cellmentioning

confidence: 99%

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Predicting experimental results for polyethylene by computer simulation

Ramos

Vega

Martínez‐Salazar

2018

European Polymer Journal

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This feature article reviews several aspects of computational approaches to polyethylene melt and solid state properties in relation to existing experimental results. Based on 40 years of experience in the field, we offer a personal view of how computer simulations are helping to understand the physics of polyethylene as a model polymer. The first issue discussed is the molten state of polyethylene, including static and dynamic properties and entanglement features along with their impacts on rheological behaviour. We then examine the glass transition, crystallization process and solid state structure, including the interlamellar region. This is followed by brief descriptions of the latest advances in simulating mechanical properties and of the various methodologies used to simulate the physics of polyethylene. Throughout the manuscript, references are made to our own work and also to studies by many other authors that have nicely contributed to developments in simulating the physics of polyethylene in close agreement with experimental results.

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Section: The Orthorhombic Unit Cellmentioning

confidence: 99%

“…It should be noted that Román-Pérez et al [251] and Wu et al [252] later described a reformulation and a simplified implementation of this scheme. Further recent refinements and improvements by other authors have been reviewed in [239].…”

Section: The Orthorhombic Unit Cellmentioning

confidence: 99%

Predicting experimental results for polyethylene by computer simulation

Ramos

Vega

Martínez‐Salazar

2018

European Polymer Journal

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“…This elastic constant relates to the stretching of the orthorhombic a-lattice parameter, which we in the present work find to be C 11 ≈ 9.0 GPa in accordance with experimental data. In addition to the aforementioned data in Table I, we have compared the obtained optimized lattice parameters for PE with those computed by Kleis et al [66] and Pham et al [67] for a wide range of nonlocal formulations. Specifically, we have compiled data for the vdW-DF [37], vdW-DF2 [77], DF-C09 [78], DF-optB88 [79], DF-optB86b [80], revDF2 [81,82], and rVV10 [83] functionals.…”

Section: A Ground State Datamentioning

confidence: 99%

Ab initioinvestigation of monoclinic phase stability and martensitic transformation in crystalline polyethylene

Olsson

Hyldgaard

Schröder

et al. 2018

Phys. Rev. Materials

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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.

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“…We incorporate van der Waals interactions with a nonlocal density functional [46][47][48] (commonly denoted vdw-DF) that captures long-range correlation and has been tested for the polyethylene crystal [49]. Others have studied the performance of various nonlocal functionals for polymer crystals [50] and found that this functional, and an updated version, performed best in estimating the a and b lattice parameters. We note that the choice of functional can affect the computed value of the thermal conductivity [51].…”

Section: Theorymentioning

confidence: 99%

Thermal transport and phonon focusing in complex molecular crystals: Ab initio study of polythiophene

2019

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Thermally conductive molecular crystals are of fundamental interest because they are unlike typical complex crystals, which conduct heat poorly owing to their large phonon scattering phase space. While molecular crystals with high thermal conductivity in the range of tens of Wm −1 K −1 have been known experimentally for decades, their intrinsic upper limits for thermal conductivity are unclear. Ab initio methods that have been successfully applied to simple crystals have proved difficult to adapt to molecular crystals due to quantum nuclear motion and their complex primitive cells. Here, we report the thermal transport properties of crystalline polythiophene with 28 atoms per primitive cell using an ab initio approach that rigorously includes finite-temperature anharmonicity and quantum nuclear effects. The calculated room temperature thermal conductivity is 198 Wm −1 K −1 along the chain axis, a high value that arises from exceptional phonon focusing along the chain for both acoustic and optical branches for nearly all wave vectors and despite short lifetimes in the picosecond range. Our finding, along with other recent ab initio studies of polyethylene, suggests that the intrinsic upper bounds for the chain axis thermal conductivity of polymer crystals may exceed 100 Wm −1 K −1 .

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Density-functional description of polymer crystals: A comparative study of recent van der Waals functionals

Cited by 15 publications

References 43 publications

Predicting experimental results for polyethylene by computer simulation

Predicting experimental results for polyethylene by computer simulation

Ab initioinvestigation of monoclinic phase stability and martensitic transformation in crystalline polyethylene

Thermal transport and phonon focusing in complex molecular crystals: Ab initio study of polythiophene

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