Presentation is loading. Please wait.

Presentation is loading. Please wait.

Workshop on HPC in India Modelling Soft Matter Balasubramanian Sundaram Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific.

Similar presentations


Presentation on theme: "Workshop on HPC in India Modelling Soft Matter Balasubramanian Sundaram Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific."— Presentation transcript:

1 Workshop on HPC in India Modelling Soft Matter Balasubramanian Sundaram Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore ATIP 1 st Workshop on HPC in SC-09

2 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-092 Current Challenge Vesicle interacting with a lipid membrane Shinoda and Klein, Science (2008) ‏

3 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-093 Molecular dynamics Obtain Forces, Integrate tt

4 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-094 Parallelization strategies  Decomposition based on particle indices (works for < 1000 particles) ‏  Domain/Spatial decomposition (for large system sizes ~ 1 million) ‏  Decomposition based on particle indices (works for < 1000 particles) ‏  Domain/Spatial decomposition (for large system sizes ~ 1 million) ‏ System of interacting particles

5 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-095 Approaches  Density functional theory based MD (ab initio molecular dynamics) ‏  Accurate, but expensive  Empirical force field based atomistic MD  Less accurate than DFT, but reasonable; not so expensive  Coarse grain MD  Softer forces, fewer degrees of freedom, ideal to study mesoscale phenomena

6 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-096 Hierarchical modelling  Perform ab initio MD (AIMD) calculations. Obtain information on intermolecular structure  Refine empirical force-field parameters so that the results of atomistic MD match those from AIMD.  Use results of atomistic MD to carry out coarse grain simulations

7 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-097 Challenges  Length and time scales of processes and phenomena are large (tens of nanometers, micro to milliseconds)  Atomistic description is crucial to understand the chemistry of specific substances  How does one build models starting from atomistic ones, to reach the large length/time scales?

8 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-098 Multiscale Modeling Atomistic Coarse Grain Ab Initio

9 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-099 Ionic compounds NaCl M.P.: 801 ºC [bmim][PF 6 ] M.P.: 10 ºC  Low volatility  Environmentally benign  Polar liquids  Nanoparticle synthesis, electrolytes, catalysis

10 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0910 Issues  Lack of scattering data to determine intermolecular structure in the liquid state  Transferability of intermolecular potentials whose partial charges are fitted to gas phase quantum calculations  Phase behaviour  Prediction of bulk properties  Microheterogeneity

11 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0911 Intermolecular structure Anions come closer due to electronic polarization B.L. Bhargava and S. Balasubramanian Journal of Physical Chemistry B 111, 4477 (2007) Atomistic (non-bonded): CLP model, JPCB (2004)

12 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0912 Refined atomistic model: Predictions  Density within 1.5% of experiment between K, within 2% up to 200 MPa  Diffusion coefficients within 20% of experiment at 300K/1atm  Surface tension at 300K within 10% of experiment  Enthalpy of vaporization within 10% of experiment B.L. Bhargava and S. Balasubramanian, J. Chem. Phys. (2007) Refining the parameters of the atomistic model to match the intermolecular structure of AIMD provides:

13 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0913 Intermolecular structure B.L. Bhargava, M.L. Klein and S. Balasubramanian, ChemPhysChem (2008)

14 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0914 Coarse graining Example: [C 7 mim][PF 6 ] 41 atoms versus 6 beads Can be used for any [C n mim][PF 6 ] Studied here: n=4, 7, 10 Parametrized for [C 4 mim][PF 6 ] Around 3 heavy atoms per bead Atom charges summed up to give bead charges Atom dispersion strengths summed up to give bead Epsilons Beads of alkyl tail: Model based on surfactants (Shinoda et al)

15 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0915 Nanoscale ordering NEUTRON X-RAY [C 4 mim][PF 6 ] [C 10 mim][PF 6 ] [C 7 mim][PF 6 ] Increasing Correlation Length Triolo et al (2008) SIMULATION EXPERIMENT BLB, RD, MLK & SB, Soft Matt. (2007)

16 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0916 Morphology Bicontinuous 12 nm Anion Rich Tail Rich BLB, RD, MLK & SB, Soft Matt. (2007)

17 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0917 Symmetric tails 1-butyl,3-methylimidazolium hexafluorophosphate 1,3-didecylimidazolium hexafluorophosphate Asymmetric tails Symmetric tails Dzyuba and Bartsch Chemcomm (2001) “The didecyl compound has two melting points: -27 o C and 16 o C” Raju and Balasubramanian, J. Mater. Chem. (2009)

18 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0918 Emergence of lamellar phase After 50 nsAfter 450 ns Sectional View: After 450 ns Lamellar Phase Self Assembly Raju and Balasubramanian, J. Mater. Chem. (2009)

19 Balasubramanian Sundaram ATIP 1 st Workshop on HPC in SC-0919 Summary  D evelopment of a hierarchical approach to model room temperature ionic liquids  Ab initio, atomistic and coarse grain simulations carried out  Quantitative comparison to experiments at each stage  We predict the formation of a lamellar phase in ionic liquids containing cations with symmetric long alkyl groups.


Download ppt "Workshop on HPC in India Modelling Soft Matter Balasubramanian Sundaram Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific."

Similar presentations


Ads by Google