Shuangxing Dai wrote:
Hi, all,
I was wondering to modify Shift electrostatic summation to a new
one. The origin Shift form in Gromacs is like 1/r-1/Rc (Rc is cut-off),
I need to modify to erfc(alpha*r)/r-erfc(alpha*Rc)/Rc, and the original
long-range correction of Shift in code shift_util.c is q^2/(2*Rc) (
something like that ), I need to
q^2*(erfc(alpha*Rc)/(2*Rc)+alpha/sqrt(pi)). So question is:
How the force to Shift was calculated? Gromacs use the differentiation
to energy, got the force formula, then calculated the force? Or just use
the numerical differentiation to the energy and got it? If is the latter
one, I do not need to modify the force calculation.
And also, the alpha for Ewald summation, is there an option or
parameters to adjust this value?
Hi, Mark and Berk, if I want do modify shift electrostatic summation as
I want, what other files or place do I need to modify, except
shift_util.c and force.c?
Shuangxing Dai
It would be wise to test everything with a table look up. Much easier,
and the better performance than analytical potentials.
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