- #1
onizuka
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Hi,
i've been doing a simulation using LJ model, but I'm having a troublesome time on figuring out, what's happening with the energy
This is the LJ potencial:
[tex]E = 4\epsilon\left[\left(\frac{\sigma}{R}\right)^{12} - \left(\frac{\sigma}{R}\right)^6\right][/tex]
but I've been using this simplified form given on Fosdick's book:
[tex]E = \left[\left(\frac{1}{R}\right)^{12} - \left(\frac{2}{R}\right)^6\right][/tex]
And for time integration I'm using the velocity Verlet method.
I am using noble gases only, and in this example, i have 3 atoms forming an equilaterum triangle. The system starts with KE = 0, and PE < 0.
What happens is that while the atoms approach each other, the KE increases (as one would expect), and the PE decreases (it is always a negative value, so it increases in absolute value).
When they are too close, they repel themselfs and the opposite happens.
So i have a kind-of "harmonic" motion, where the [tex]E[/tex] increases and decreases.
To give you an idea of the values i have, i initially have an [tex]E[/tex] = -0.00051 and can go up to [tex]E[/tex] = -0.3619
My suspection of why this doesn't work migth be because of the values I'm using in the simulation. (and yes... i really don't know what is the magnitude of the SI units i am using here... much less the ones i should be using :shy: )
time step = 0.01
particle mass = 1
radius = 0.6
distance between each particle = 5
I've read that using the conservation of energy, one can do some corrections on the values obtained... but uhh, i think what i have here i something completely different.
Thanks in advance for any help.
i've been doing a simulation using LJ model, but I'm having a troublesome time on figuring out, what's happening with the energy
This is the LJ potencial:
[tex]E = 4\epsilon\left[\left(\frac{\sigma}{R}\right)^{12} - \left(\frac{\sigma}{R}\right)^6\right][/tex]
but I've been using this simplified form given on Fosdick's book:
[tex]E = \left[\left(\frac{1}{R}\right)^{12} - \left(\frac{2}{R}\right)^6\right][/tex]
And for time integration I'm using the velocity Verlet method.
I am using noble gases only, and in this example, i have 3 atoms forming an equilaterum triangle. The system starts with KE = 0, and PE < 0.
What happens is that while the atoms approach each other, the KE increases (as one would expect), and the PE decreases (it is always a negative value, so it increases in absolute value).
When they are too close, they repel themselfs and the opposite happens.
So i have a kind-of "harmonic" motion, where the [tex]E[/tex] increases and decreases.
To give you an idea of the values i have, i initially have an [tex]E[/tex] = -0.00051 and can go up to [tex]E[/tex] = -0.3619
My suspection of why this doesn't work migth be because of the values I'm using in the simulation. (and yes... i really don't know what is the magnitude of the SI units i am using here... much less the ones i should be using :shy: )
time step = 0.01
particle mass = 1
radius = 0.6
distance between each particle = 5
I've read that using the conservation of energy, one can do some corrections on the values obtained... but uhh, i think what i have here i something completely different.
Thanks in advance for any help.
Last edited: