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| This is part of the multicolvar module |
Calculate whether or not a set of torsional angles are within a particular range.
When the label of this action is used as the input for a second you are not referring to a scalar quantity as you are in regular collective variables. The label is used to reference the full set of quantities calculated by the action. This is usual when using MultiColvar functions. Generally when doing this the previously calculated multicolvar will be referenced using the DATA keyword rather than ARG.
This Action can be used to calculate the following scalar quantities directly. These quantities are calculated by employing the keywords listed below. These quantities can then be referenced elsewhere in the input file by using this Action's label followed by a dot and the name of the quantity. Some of them can be calculated multiple times with different parameters. In this case the quantities calculated can be referenced elsewhere in the input by using the name of the quantity followed by a numerical identifier e.g. label.lessthan-1, label.lessthan-2 etc. When doing this and, for clarity we have made it so that the user can set a particular label for each of the components. As such by using the LABEL keyword in the description of the keyword input you can customize the component name
| Quantity | Keyword | Description |
| between | BETWEEN | the number/fraction of values within a certain range. This is calculated using one of the formula described in the description of the keyword so as to make it continuous. You can calculate this quantity multiple times using different parameters. |
| ATOMS | the atoms involved in each of the torsion angles you wish to calculate. Keywords like ATOMS1, ATOMS2, ATOMS3,... should be listed and one torsion will be calculated for each ATOM keyword you specify (all ATOM keywords should provide the indices of four atoms). The eventual number of quantities calculated by this action will depend on what functions of the distribution you choose to calculate. You can use multiple instances of this keyword i.e. ATOMS1, ATOMS2, ATOMS3... |
| NUMERICAL_DERIVATIVES | ( default=off ) calculate the derivatives for these quantities numerically |
| NOPBC | ( default=off ) ignore the periodic boundary conditions when calculating distances |
| SERIAL | ( default=off ) do the calculation in serial. Do not use MPI |
| LOWMEM | ( default=off ) lower the memory requirements |
| TIMINGS | ( default=off ) output information on the timings of the various parts of the calculation |
| BETWEEN | calculate the number of values that are within a certain range. These quantities are calculated using kernel density estimation as described on histogrambead. The final value can be referenced using label.between. You can use multiple instances of this keyword i.e. BETWEEN1, BETWEEN2, BETWEEN3... The corresponding values are then referenced using label.between-1, label.between-2, label.between-3... |
| HISTOGRAM | calculate how many of the values fall in each of the bins of a histogram. This shortcut allows you to calculates NBIN quantities like BETWEEN. The final value can be referenced using label.histogram. You can use multiple instances of this keyword i.e. HISTOGRAM1, HISTOGRAM2, HISTOGRAM3... The corresponding values are then referenced using label.histogram-1, label.histogram-2, label.histogram-3... |
The following provides an example of the input for the TORSIONS command
TORSIONS ... ATOMS1=168,170,172,188 ATOMS2=170,172,188,190 ATOMS3=188,190,192,230 BETWEEN={GAUSSIAN LOWER=0 UPPER=pi SMEAR=0.1} LABEL=ab ... TORSIONS PRINT ARG=ab.* FILE=colvar STRIDE=10
Writing out the atoms involved in all the torsion angles in this way can be rather tedious. Thankfully if you are working with protein you can avoid this by using the MOLINFO command. PLUMED uses the pdb file that you provide to this command to learn about the topology of the protein molecule. This means that you can specify torsion angles using the following syntax:
#SETTINGS MOLFILE=regtest/basic/rt32/helix.pdb MOLINFO MOLTYPE=protein STRUCTURE=myprotein.pdb TORSIONS ... ATOMS1=@phi-3 ATOMS2=@psi-3 ATOMS3=@phi-4 BETWEEN={GAUSSIAN LOWER=0 UPPER=pi SMEAR=0.1} LABEL=ab ... TORSIONS PRINT ARG=ab.* FILE=colvar STRIDE=10
Here, @phi-3 tells plumed that you would like to calculate the \(\phi\) angle in the third residue of the protein. Similarly @psi-4 tells plumed that you want to calculate the \(\psi\) angle of the fourth residue of the protein.
1.8.14