Re: Re: want to modify NDSolve--molecular dynamics with mathematica
- To: mathgroup at smc.vnet.net
- Subject: [mg26375] Re: [mg26365] Re: want to modify NDSolve--molecular dynamics with mathematica
- From: Richard Gass <gass at physics.uc.edu>
- Date: Sat, 16 Dec 2000 02:40:08 -0500 (EST)
- References: <90v82t$79m@smc.vnet.net> <200012130741.CAA17214@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
There is a little known option to NDSolve called "StoppingTest". Rob
Knapp talked about this option is his talk on NDSolve at the last
developers conference. I believe that you can use StoppingTest to
stop the solution when x[t]>a0 . You can then restart NDSolve after
you have moved the atom.
Jens-Peer Kuska wrote:
>Hi,
>
>you can write your equation with Mod[x[t],a0]
>but it will make the InterpolatingFunction[]s
>returned by NDSolve[] unusable. Because
>x[t] will jump back to for x>a0 and the
>interpolation is useless.
>
>You must write your own initial value solver.
>
>Regards
> Jens
>
>
>"Toshiyuki (Toshi) Meshii" wrote:
>>
>> Hello,
>>
>> I was wondering whether I can apply NDSolve to molecular dynamics, on the
>> standpoint of periodical boundary condition.
>>
>> The eqation I want to solve is the simple Newton equation (Let me simplify
>> the problem).
>> m D[x, {x,2}] == F
>> However, periodical boundary condition makes it difficult to apply NDSolve.
>> That is, once
>> 0<x[t]<a0
>> is not satisfied (a0 is a constant), I have to move the atom so that this
>> condition is satisfied.
>> In concrete,
>> if x[t]<0 ---> x[t]=x[t]+a0
> > if x[t]>a0 ---> x[t]=x[t]-a0
>> and then restart to solve the equation.
>>
>> Is there any way to realize this by directly applying NDSolve?
>> If not, how can I modify NDSolve?
>>
>> -Toshi
--
Richard Gass
Department of Physics
University of Cincinnati
Cincinnati, OH 45221
phone- 513-556-0519
E-Mail gass at physics.uc.edu
- References:
- Re: want to modify NDSolve--molecular dynamics with mathematica
- From: Jens-Peer Kuska <kuska@informatik.uni-leipzig.de>
- Re: want to modify NDSolve--molecular dynamics with mathematica