Energetics and Mechanics of Human Running on Surfaces of Different Stiffnesses
Quantum Mechanics and Molecular Mechanics Studies on Energetics and Nucleation
description
Transcript of Quantum Mechanics and Molecular Mechanics Studies on Energetics and Nucleation
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)