quantum mechanics and molecular mechanics studies on energetics and nucleation
DESCRIPTION
D b. . b. c. a. y. x. e. S xx. y. S yy. S xy. x. PVDF. P(VDF-TrFE). - PowerPoint PPT PresentationTRANSCRIPT
Multi-Scale Modeling of Electro-Active Polymers: Towards Computational Materials Design Haibin Su, Alejandro Strachan (LANL), Tahir Cagin, Albert Cuitino (Rutgers) & William A. Goddard III
Materials and Process Simulation Center, Beckman Institute, California Institute of Technology, Pasadena, California 91125
Quantum Mechanics and Molecular Mechanics Studies on Energetics and Nucleation Meso-Macro-Scale Modeling on Phase Transformation
SeqQuest code (P. Schultz, SNL), DFT, GGA-PBE, pseudopotentials, Gaussian basis set
( Energy in kcal / mole per carbon )
Phase I: All Trans Phase II TGTG’ Phase III T3GT3G’
An
gle
(deg
ree)
An
gle
(deg
ree)
Torsional angle (degree) Torsional angle (degree)
C C C0 +2-1-2
Restraint is applied to bond 0
Perpendicular to the chains
strain rate (1010 1/s)
Sh
ear
Str
ess
(GP
a)
xy
Strain rate 3.85 x 1010 (1/s)
yz
xz
Perpendicular to the chains
xy
yz
Along the chains
Perpendicular to the chains
Along the chains
Db
/E
-0.05 0 0.05 0.1
-0.08
-0.04
0
0.04
0.08
0.12
0.16
1
1
2
2
3
3
Phase transformation from non-polar to polar (polarization) Phase transformation from non-polar to polar (polarization) driven by applied strain for a driven by applied strain for a single nucleationsingle nucleation site site
ab initio QMEoS of various phasesTorsional barriersVibrational frequencies
Force Fields and MDElastic, dielectric constantsNucleation BarrierDomain wall and interface mobilityPhase transitionsAnisotropic Viscosity
Meso- Macro-scaleNanostructure-properties relationshipsConstitutive Laws
Multi-Scale-Modeling Roadmap
Initial conditionNon-polar
Load
Mechanically driven non-polar (T3G) to polar (all-trans) transformation
ALLOWS FOR ARBITRARY SHAPES AND GENERAL
ELECTROMECHANICAL BC IN 2D and 3D
Complex nucleation of polar phase
Undeformed Deformed
(T3G)
(all-trans)
Nucleation of a G bond in an all-T Configuration
PVDF
P(VDF-TrFE)
En
ergy
( k
cal /
mol
)
Torsional angle (degree)
+1C C C
•Torsions of bonds +1 and -1 remain ~180° •Intrinsic Conservation of Torsion Angles
Stress (Gpa)
Mob
ilit
y (
m/s
)
Polar (all trans) Non-Polar (T3G)
time = 0 ps time = 3 ps
time = 6 ps
Almost completely polar
time = 9 ps
Molecular Dynamics Studies on Interface Mobility and Chain Sliding
0 5 10Time (ps)
15 20 25 30
0.4
0.3
0.2
0.1
0
0.5
Sh
ear
Str
ess
(GP
a)
-0.2
-0.1
0.16
0.14
0.12
0.10
0.08
0.009
0.029
1.8 2.8 3.8 4.8 5.8 6.8
Along the chains
Perpendicular to the chains
Vis
cosi
ty (
Pa.
s)
2.0 3.0 4.0 5.0 6.0 7.0
0.00050
0.00055
0.00060
0.00065
0.0020
0.0025
0.0030
0.0035
0.0040
Sxxe
Syy Sxy
y
x
x
y
cb
a
Represents ferroelectric phase
yx
Strain ()
Energ
y(J)
0 0.02 0.04 0.060
5E+06
1E+07
1.5E+07
30% polarized
20%
Strain ()
strain rate (1010 1/s)
• Eulerian code
• Coupled electromechanical response
• Long-range interaction
• Hierarchical Multiscale: Parameters obtained from atomistics
• Interface tracking – level set
• Nucleating mechanism with G0 Energy Barrier
• Propagation mechanism driven by global minimization of
Gibbs free energy – Gm (Energy Barrier for motion)