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Volumn 121, Issue 10, 2004, Pages 4941-4950

Simulation of the plastic behavior of amorphous glassy bis-phenol-A- polycairbonate

Author keywords

[No Author keywords available]

Indexed keywords

ACTIVATION ENERGY; CHEMICAL BONDS; COMPUTATIONAL METHODS; COMPUTER SIMULATION; ELASTIC MODULI; GLASS; KINETIC THEORY; MOLECULAR DYNAMICS; OPTIMIZATION; PERCOLATION (FLUIDS); PHENOLS; RELAXATION PROCESSES; SHEAR FLOW; STRAIN RATE;

EID: 4544313845     PISSN: 00219606     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.1778157     Document Type: Article
Times cited : (16)

References (86)
  • 38
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    • San Diego: Accelrys Inc
    • Aecelrys Inc., CERIUS2, Release 4.0, San Diego: Accelrys Inc., 1999.
    • (1999) CERIUS2, Release 4.0
  • 41
    • 4544336544 scopus 로고    scopus 로고
    • note
    • The multistep algorithm of the ORAC program proved very useful in speeding up the MD simulations, allowing one to use a time step of 10 fsec at 300 K and 4.5 fsec at 1500 K.
  • 42
    • 4544297998 scopus 로고    scopus 로고
    • Courtesy of Dr. G. Marchetti and Dr. M. Marchi (Orsay, France)
    • Courtesy of Dr. G. Marchetti and Dr. M. Marchi (Orsay, France).
  • 43
    • 4544311527 scopus 로고    scopus 로고
    • Accelrys Inc., San Diego
    • Accelrys Inc., MATERIALS STUDIO, Release 2.1 (Accelrys Inc., San Diego, 2002).
    • (2002) MATERIALS STUDIO, Release 2.1
  • 44
    • 4544246849 scopus 로고    scopus 로고
    • note
    • Results analogous to those described below were found when using different starting configurations, obtained by annealing the system at 1500 K for longer times.
  • 45
    • 4544323593 scopus 로고    scopus 로고
    • note
    • The Discover® program does not allow one to perform "strained" energy minimizations - i.e., minimizations in which one value of the cell parameter is held fixed, while the others are optimized, or "strained" MD simulations - i.e., in which one value of the cell parameters is held fixed while the others are allowed to vary, following the Parrinello-Rahman dynamics (see Ref, 20).
  • 46
    • 4544352504 scopus 로고    scopus 로고
    • note
    • We chose a small value of the fictitious cell mass to increase the speed of approaching equilibrium in the MD runs. A discussion of the optimal value of the fictitious cell mass is deferred to future work.
  • 47
    • 4544387478 scopus 로고    scopus 로고
    • note
    • This may be thought of as corresponding to a sequence of creep steps at increasing stress levels (Ref. 48) conducted at a very high strain speed.
  • 57
    • 4544385291 scopus 로고    scopus 로고
    • note
    • Other structures exibit strain hardening at larger values of strain.
  • 59
    • 4544324555 scopus 로고    scopus 로고
    • note
    • The new structure obtained by bringing a given ideal structure outside its range of elastic behavior can be used as the configuration of subsequent MD simulations plus "sweeping procedures" to generate other ideal structures, somewhat related to (but not identical with) the original one.
  • 60
    • 4544270645 scopus 로고    scopus 로고
    • note
    • One can easily devise more rigorous procedures to attain this result, such as local variants of global optimization techniques, etc. (Ref. 30). The "ideal structures" are in fact representative of "catchment basins" within which ergodicity is recovered in the glassy state, with a stability (entropic component of the free energy) proportional to the volume of the phase space associated with them. The sweeping procedure can be seen as a rough but very economical and (in the present case) rather efficient approximate version of these general approaches.
  • 61
    • 4544236663 scopus 로고    scopus 로고
    • note
    • Those rearrangements which are only weakly coupled to the overall strain cannot be discriminated by the sweeping procedure, but they are also less interesting in this context, as they represent "floppy" local modes of "soft" regions of the system.
  • 63
    • 4544336543 scopus 로고    scopus 로고
    • note
    • The Polak-Ribière (Réf. 64) algorithm (a conjugate gradient method) was used for the energy minimizations, with a stopping criterion for maximum derivative of 0.01 kcal/mol/Å.
  • 65
    • 4544385290 scopus 로고    scopus 로고
    • note
    • The Discover® program does not allow one to calculate the Hessian matrix for a system of 10 000 atoms, so that we were unable to implement the normal-mode analysis of Ref. 32.
  • 67
    • 4544313869 scopus 로고    scopus 로고
    • note
    • Actually, this reasonable assumption brings us outside the original formulation of the Eyring model (Ref. 66).
  • 74
    • 4544224661 scopus 로고    scopus 로고
    • note
    • In the case that the cell parameters are different, the choice of a threshold value allows us to get rid of spurious effects due to the difference between affine transformation and elastic response. Better results could be obtained by keeping stiff intramolecular degrees of freedom rigid.
  • 75
    • 4544263368 scopus 로고    scopus 로고
    • note
    • A rough "coarse-grained" check was also performed, by monitoring which phenyl-carbonate-phenyl7 segments underwent a syn-anti conformational transition.
  • 76
    • 4544339238 scopus 로고    scopus 로고
    • note
    • It can be noted that the Discover® program does not calculate atomic stresses (as defined in Ref. 11). They can be obtained via numerical differentiation of the atomic energies, without, however, conveying substantially new information in the present case.
  • 77
    • 4544313870 scopus 로고    scopus 로고
    • note
    • The average length of these segments was about two to three monomeric units, with a maximum length of ten units.
  • 78
    • 4544277973 scopus 로고    scopus 로고
    • note
    • From previous work (Ref. 16), it is known that in BPA-PC each barrier typically has an activation energy of several kcal/mol, and there are 80 of such motions.
  • 79
    • 4544320867 scopus 로고    scopus 로고
    • A. Fortunelli, C. Geloni, A. Lazzeri, and G. Marchetti (unpublished)
    • A. Fortunelli, C. Geloni, A. Lazzeri, and G. Marchetti (unpublished).
  • 81
    • 0002142597 scopus 로고    scopus 로고
    • edited by F. Bethuel, G. Huisken, S. Müller, K. Steffen, K. Hildebrandt, and M. Struwe (Springer, Berlin)
    • S.Müller, in Calculus of Variations and Geometric Evolution Problems, edited by F. Bethuel, G. Huisken, S. Müller, K. Steffen, K. Hildebrandt, and M. Struwe (Springer, Berlin, 1999).
    • (1999) Calculus of Variations and Geometric Evolution Problems
    • Müller, S.1


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.