From: Brian Radak (bradak_at_anl.gov)
Date: Mon Oct 03 2016 - 21:16:58 CDT
This is (somewhat regrettably) implemented in multiple places in the
code - often piecewise. The function is:
S(r) = (r2^2 - r^2)^2 * (r2^2 - 3*r1^2 + 2*r^2) / (r2^2 - r1^2)^3
on the interval (r1, r2) where r1 = switchdist and r2 = cutoff (the
latter are the NAMD keyword names).
This is a sixth order polynomial, but I believe it is something like a
third order Chebyshev polynomial expansion of tan(2*x-1) when x is taken
as (r^2 - r1^2) / (r2^2 - r1^2) (or something similar)
On 10/02/2016 11:57 PM, Faramarz Joodaki wrote:
> Hi everyone!
> I would be so grateful if you could tell me what is the exact switch function formula for non-bonded interaction in NAMD?
> Thank you!
> Best Regards,
-- Brian Radak Postdoctoral Appointee Leadership Computing Facility Argonne National Laboratory 9700 South Cass Avenue, Bldg. 240 Argonne, IL 60439-4854 (630) 252-8643 brian.radak_at_anl.gov
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