Transcript Document

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
Molecular Dynamics Studies on Interface Mobility and Chain Sliding
Perpendicular to the chains
Polar (all trans) Non-Polar (T3G)
Meso- Macro-scale
Nanostructure-properties
relationships
Constitutive Laws
time = 0 ps
0.5
Shear Stress (GPa)
Multi-Scale-Modeling Roadmap
time = 3 ps
Along the chains
Almost completely polar
Strain rate 3.85 x 1010 (1/s)
0.4
0.3
Perpendicular to the chains
0.2
0.1
xz
yz
0
-0.1
xy
-0.2
0
5
10
15
25
20
Time (ps)
xy
0.16
time = 6 ps
time = 9 ps
0.14
Shear Stress (GPa)
0.0040
Viscosity (Pa.s)
ab initio QM
EoS of various phases
Torsional barriers
Vibrational frequencies
Mobility ( m/s )
0.0035
Force Fields and MD
Elastic, dielectric constants
Nucleation Barrier
Domain wall and interface
mobility
Phase transitions
Anisotropic Viscosity
30
0.0030
Perpendicular to the chains
0.0025
0.0020
0.00065
0.12
Perpendicular to the chains
0.10
0.08
yz
0.029
0.00060
Along the chains
0.00055
Along the chains
0.009
0.00050
2.0
3.0
4.0
strain rate
Stress (Gpa)
5.0
(1010
6.0
1.8
7.0
2.8
3.8
4.8
5.8
6.8
strain rate (1010 1/s)
1/s)
Quantum Mechanics and Molecular Mechanics Studies on Energetics and Nucleation
Meso-Macro-Scale Modeling on Phase Transformation
Nucleation of a G bond in an all-T Configuration
Db
• Eulerian code
Phase II TGTG’
Phase III T3GT3G’
b
• Coupled electromechanical response
Energy ( kcal / mol )
Phase I: All Trans
PVDF
a
• Nucleating mechanism with G0 Energy Barrier
Sxy
x
Energy ( J )
Represents ferroelectric phase
5E+06
•Torsions of bonds +1 and -1 remain ~180°
•Intrinsic Conservation of Torsion Angles
0
0
0.02
0.04
Strain ()
0.12
ALLOWS FOR ARBITRARY
SHAPES AND GENERAL
ELECTROMECHANICAL
BC IN 2D and 3D
0.06
Strain ()
0.16
Angle (degree)
Angle (degree)
Syy
1E+07
3
2
Mechanically driven non-polar (T3G)
to polar (all-trans) transformation
Load
Initial condition
Non-polar
1
(T3G)
0.08
0.04
Undeformed
1
-0.05 2
3
Torsional angle (degree)
x
1.5E+07

-2 -1 0 +1 +2
C C C C C C
Sxx
y
20%
( Energy in kcal / mole per carbon )
e
y
• Interface tracking – level set
• Propagation mechanism driven by
global minimization of
Gibbs free energy – Gm (Energy Barrier for motion)
Torsional angle (degree)
Restraint is applied to bond 0
x
• Hierarchical Multiscale: Parameters obtained from atomistics
P(VDF-TrFE)
c
y
• Long-range interaction
30% polarized
SeqQuest code (P. Schultz, SNL), DFT, GGA-PBE, pseudopotentials, Gaussian basis set
Phase transformation from non-polar to polar (polarization)
 driven by applied strain for a single nucleation site
Torsional angle (degree)
0
0
-0.04
-0.08
0.05
(all-trans)
Deformed
0.1
/E
Complex nucleation of polar phase