request

Dear all

I have an ionic liquid with polar side chain length and I want to equilibrate my system. Since ILs are viscous and slow, equilibration of IL simulation box is not as easy as it is for normal solvents. When I use NPT condition to equilibrate my system, I see that density of my system (1.55gr/cm3) at 292 K is somewhat farther than experimental density (1.32gr/cm3) at 292 K. but when the temperature is high (500-600 K), density is very near to experimental density, although I cannot see this density at 292 K. maybe the problem is polarity of my system and I should cool down my system from 500-600 K to 292 K. Some guys suggested some ways to equilibrate my system. For example, in order to equilibriate IL systems, I should first run my simulations at higher temperature e.g. 500-600K with scaled charges (0, 10, 20, 50% of the full atomic charges) and then later I should slowly decrease the temperature to reach at 292K and increase the charges to 100%. I don’t know how I can scale my charges in lammps. I appreciate if somebody can give me a solution for my problem.

Cheers

Mehdi shakourian

Dear all

I have an ionic liquid with polar side chain length and I want to
equilibrate my system. Since ILs are viscous and slow, equilibration of IL
simulation box is not as easy as it is for normal solvents. When I use NPT
condition to equilibrate my system, I see that density of my system
(1.55gr/cm3) at 292 K is somewhat farther than experimental density
(1.32gr/cm3) at 292 K. but when the temperature is high (500-600 K), density
is very near to experimental density, although I cannot see this density at
292 K. maybe the problem is polarity of my system and I should cool down my
system from 500-600 K to 292 K. Some guys suggested some ways to equilibrate
my system. For example, in order to equilibriate IL systems, I should first
run my simulations at higher temperature e.g. 500-600K with scaled charges
(0, 10, 20, 50% of the full atomic charges) and then later I should slowly
decrease the temperature to reach at 292K and increase the charges to 100%.
I don’t know how I can scale my charges in lammps. I appreciate if somebody
can give me a solution for my problem.

Check out the "set" command. For example:

set type 3 charge 0.5

http://lammps.sandia.gov/doc/set.html

Cheers

Cheers

Dear all

I have an ionic liquid with polar side chain length and I want to
equilibrate my system. Since ILs are viscous and slow, equilibration of IL
simulation box is not as easy as it is for normal solvents. When I use NPT
condition to equilibrate my system, I see that density of my system
(1.55gr/cm3) at 292 K is somewhat farther than experimental density
(1.32gr/cm3) at 292 K. but when the temperature is high (500-600 K), density
is very near to experimental density, although I cannot see this density at
292 K. maybe the problem is polarity of my system and I should cool down my
system from 500-600 K to 292 K. Some guys suggested some ways to equilibrate
my system. For example, in order to equilibriate IL systems, I should first
run my simulations at higher temperature e.g. 500-600K with scaled charges
(0, 10, 20, 50% of the full atomic charges) and then later I should slowly
decrease the temperature to reach at 292K and increase the charges to 100%.
I don’t know how I can scale my charges in lammps. I appreciate if somebody
can give me a solution for my problem.

Check out the "set" command. For example:

set type 3 charge 0.5

http://lammps.sandia.gov/doc/set.html

...and check out using fix adapt, which can do lots of nifty things.

axel.