| {In order to avoid the FEP ``end-point catastrophe", it is often important to make sure that a growing particle does not have an unbounded potential right at the moment that it is created (in case that it appears on top of another particle). One way to deal with this for electrostatic interactions, is to allow a bounded scaled vdW potential (using a positive {\tt fepVdWShiftCoeff}) to first repel all overlapping particles at low values of $\lambda$. As $\lambda$ increases, once the particles are repelled, it is now safe to turn on FEP electrostatics. {\tt fepElecLambdaStart} is the value of the scaling factor $\lambda$ at which electrostatic interactions are turned on and start ramping up linearly; below this value, electrostatics are turned off for all FEP particles. Note: what is really being modified is the $\lambda$ factor that directly multiplies the interactions (\emph{i.e.}, 0 = fully off, 1 = fully on), rather than the $\lambda$ provided by the user, which may sometimes correspond to (1 - $\lambda$).} | {In order to avoid the FEP ``end-point catastrophe", it is often important to make sure that a growing particle does not have an unbounded potential right at the moment that it is created (in case that it appears on top of another particle). One way to deal with this for electrostatic interactions, is to allow a bounded scaled vdW potential (using a positive {\tt fepVdWShiftCoeff}) to first repel all overlapping particles at low values of $\lambda$. As $\lambda$ increases, once the particles are repelled, it is now safe to turn on FEP short-range electrostatics. {\tt fepElecLambdaStart} is the value of the scaling factor $\lambda$ at which electrostatic interactions are turned on and start ramping up linearly; below this value, electrostatics are turned off for all FEP particles. {\tt fepElecLambdaStart} only applies to short-range electrostatics (and does not affect the computation of PME, which will scale linearly between 0 and 1 over the entire range of $\lambda$). Note: what is really being modified is the $\lambda$ factor that directly multiplies the interactions (\emph{i.e.}, 0 = fully off, 1 = fully on), rather than the $\lambda$ provided by the user, which may sometimes correspond to (1 - $\lambda$).} |