.. index:: newton newton command ============== Syntax """""" .. parsed-literal:: newton flag newton flag1 flag2 * flag = *on* or *off* for both pairwise and bonded interactions * flag1 = *on* or *off* for pairwise interactions * flag2 = *on* or *off* for bonded interactions Examples """""""" .. parsed-literal:: newton off newton on off Description """"""""""" This command turns Newton's 3rd law *on* or *off* for pairwise and bonded interactions. For most problems, setting Newton's 3rd law to *on* means a modest savings in computation at the cost of two times more communication. Whether this is faster depends on problem size, force cutoff lengths, a machine's compute/communication ratio, and how many processors are being used. Setting the pairwise newton flag to *off* means that if two interacting atoms are on different processors, both processors compute their interaction and the resulting force information is not communicated. Similarly, for bonded interactions, newton *off* means that if a bond, angle, dihedral, or improper interaction contains atoms on 2 or more processors, the interaction is computed by each processor. LIGGGHTS(R)-PUBLIC should produce the same answers for any newton flag settings, except for round-off issues. With :doc:`run_style ` *respa* and only bonded interactions (bond, angle, etc) computed in the innermost timestep, it may be faster to turn newton *off* for bonded interactions, to avoid extra communication in the innermost loop. Restrictions """""""""""" The newton bond setting cannot be changed after the simulation box is defined by a :doc:`read_data ` or :doc:`create_box ` command. Some commands may not support newton "on". You will see an error message in this case when running the simulation. Related commands """""""""""""""" :doc:`run_style ` respa Default """"""" .. parsed-literal:: newton on .. _liws: http://www.cfdem.com .. _ld: Manual.html .. _lc: Section_commands.html#comm