Shock Simulations - University of Southern California · 2018-03-04 · Shock Simulation Hands-on:...
Transcript of Shock Simulations - University of Southern California · 2018-03-04 · Shock Simulation Hands-on:...
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Shock Simulations Pankaj Rajak
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Outline
Ø Shock simulation setup in water
Ø Analysis of the simulation result
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Step 1a: Create water systemand define force field
220Å
62Å
62Å
System Size: 60Å×60Å×220Å
unit realBoundary p p pread_data water.data
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Step 1b: Create water systemand define force field
220Å
62Å
62Å
System Size: 62Å×62Å×220Å
pair_style lj/cut/tip4p/long 2 1 1 1 0.1546 8.50kspace_style pppm/tip4p 1.0e-5
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Step 2: Heat the system to 300K in NVT
Velocity all create 10.00 156 mom yes rot yes dist gaussianfix 1 all npt temp $T1 $T2 100.0 iso $P1 $P2 1000timestep 2.0 fsrun 50000
2a. Initialize velocities of atoms at 10K 2b. Heat to 300K and 1 atm in NPT
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Step 2: Heat the system to 300K in NVT
Velocity all create 10.00 156 mom yes rot yes dist gaussianfix 1 all npt temp $T1 $T2 100.0 iso $P1 $P2 1000 timestep 2.0 fsrun 50000
2a. Initialize velocities of atoms at 10K 2b. Heat to 300K using Nose-Hoover thermostat
Temperature profile during heating
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Step 3: Relax the system in NVE
fix 1 all nvetimestep 2.0fsrun 50000
Relax the system so that temperature and energy becomes constant
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Step 3: Relax the system in NVE
fix 1 all nvetimestep 2.0fsrun 50000
Relax the system so that temperature and energy becomes constant
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Step 4: Shock Simulation Setup
Remove periodic boundary condition from z direction Put momentum mirror at Z= 0Å
mom
entu
m m
irro
r
Z
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Step 4: Shock Simulation Setup
mom
entu
m m
irro
r
Z
change_box all boundary p p sfix wallr all wall/reflect zhi EDGE units box
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Step 5: Shock Simulation in water
velocity all set NULL NULL 1Km/sec
mom
entum m
irror
Give all atoms 1 km/sec velocity along +Z direction
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Step 5: Shock Simulation in waterm
omentum
mirror
Reduce time-step to 0.1fs and run under NVE for 60000 steps
timestep 0.1fsrun 10000
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Step 6: Shock Simulation in water
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Shock Simulation Hands-on:
Copy the shock simulation hands-on to your staging directory.cp –r ~magics35/magics/shock-demo.tar.gz .tar xvfz shock-demo.tar.gz
cd shock-demols
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Shock Simulation Hands-on:
Go to the folder shock-demo and submit a job for 10000 stepsØ qsub job.pbs
File description:in.waterrelax (in relax folder) : creates a relaxed configurationin.shock : does shock simulation and takes input.restart as input data which is generated by in.relax
Note: water.restart is already generated for you by running in.waterrelax from relax folder
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Step 7: Temperature profile
Shock propagation
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Computational Challenges in Shock Simulation
Issue 1: Most interaction potential are fitted for low temperature and pressureExample : SB potential for RDX is attractive at very small interatomic distance
Solution: Add repulsive wall in interaction potential at small distance
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Computational Challenges in Shock Simulation
Issue 2: Due to the change in density of atoms inside simulation box during simulation, you simulation will speed will slow down
Solution: Dynamic Load balancing