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of 1.0). If the <I>dihedral</I> keyword is specified as <I>no</I> which is the
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default, then the 2,5 interaction will also be weighted by 0.5.
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<P>The <I>extra</I> keyword is used when additional bonds will be created
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<P>The <I>extra</I> keyword can be used when additional bonds will be created
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during a simulation run, e.g. by the <A HREF = "fix_bond_create.html">fix
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bond/create</A> command. It can also be used if
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molecules will be added to the system, e.g. via the <A HREF = "fix_deposit.html">fix
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deposit</A>, or <A HREF = "fix_pour.html">fix pour</A> commands, which
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will have atoms with more special neighbors than any atom in the
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current system has. A list of 1-2,1-3,1-4 neighbors for each atom is
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calculated and stored by LAMMPS. If new bonds are created (or
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molecules added with atoms with more special neighbors), the list
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needs to grow. Using the <I>extra</I> keyword leaves empty space in the
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list for N additional bonds to be added. If you do not do this, you
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may get an error when bonds (or molecules) are added.
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<P>IMPORTANT NOTE: LAMMPS stores and maintains a data structure with a
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list of the 1st, 2nd, and 3rd neighbors of each atom (within the bond
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topology of the system). If new bonds are created (or molecules added
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containing atoms with more special neighbors), the size of this list
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needs to grow. Note that adding a single bond always adds a new 1st
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neighbor but may also induce *many* new 2nd and 3rd neighbors,
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depending on the molecular topology of your syste. Using the <I>extra</I>
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keyword leaves empty space in the list for this N additional 1st, 2nd,
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or 3rd neighbors to be added. If you do not do this, you may get an
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error when bonds (or molecules) are added.
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<P>IMPORTANT NOTE: If you reuse this command in an input script, you
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should set all the options you need each time. This command cannot be