Syntax: +
+fix ID group-ID adapt N keyword values ... ++
pair args = pstyle param I J variable + pstyle = pair style name, e.g. lj/cut + pparam = parameter to adapt over time + I,J = type pair(s) to set parameter for + pvariable = name of variable that calculates value of parameter + atom args = param variable + aparam = parameter to adapt over time + avariable = name of variable that calculates value of parameter ++ +
Examples: +
+fix 1 all adapt 1 pair soft a 1 1 prefactor +fix 1 all adapt 1 pair soft a 2* 3 prefactor +fix 1 all adapt 1 pair soft a * * prefactor soft a 3 3 prefactor2 +fix 1 all adapt 10 atom diameter size ++
Description: +
+Change or adapt one or more specific simulation settings over time as +a simulation runs. Pair potential and atom attribute parameters which +can be varied by this fix are discussed below. Many other fixes can +also be used to time-vary simulation parameters, e.g. the "fix deform" +command will change the simulation box size/shape and the "fix move" +command will change atom positions and velocities in prescribed +manners. +
+The pair keyword enables various parameters of potentials defined by +the pair_style command to be changed, if the pair +style supports it. The pstyle argument is the name of the pair +style. If pair_style hybrid or hybrid/overlay is +used, pstyle should be a sub-style name. For example, pstyle +could be specified as "soft" or "lubricate". The pparam argument is +the name of the parameter to change. This is the current list of pair +styles and parameters that can be varied by this fix. See the doc +pages for individual pair styles for the meaning of these parameters. +
+ + +Some parameters are global settings for the pair style, e.g. the +viscosity setting "mu" for pair_style lubricate. +Other parameters apply to pairs of atom types within the pair style, +e.g. the prefactor "a" for pair_style soft. If a +type pair parameter is specified, the I and J settings should be +specified to indicate which pair(s) to apply it to. +
+Similar to the pair_coeff command, I and J can be +specified in one of two ways. Explicit numeric values can be used for +each, as in the 1st example above. I <= J is required. LAMMPS sets +the coefficients for the symmetric J,I interaction to the same values. +
+A wild-card asterisk can be used in place of or in conjunction with +the I,J arguments to set the coefficients for multiple pairs of atom +types. This takes the form "*" or "*n" or "n*" or "m*n". If N = the +number of atom types, then an asterisk with no numeric values means +all types from 1 to N. A leading asterisk means all types from 1 to n +(inclusive). A trailing asterisk means all types from n to N +(inclusive). A middle asterisk means all types from m to n +(inclusive). Note that only type pairs with I <= J are considered; if +asterisks imply type pairs where J < I, they are ignored. +
+If a global parameter is specified, the I and J settings still +need to be specified, but are ignored. +
+The pvariable argument is the name of an equal-style +variable which will be evaluated each time this fix is +invoked to set the parameter to a new value. Equal-style variables +can specify formulas with various mathematical functions, and include +thermo_style command keywords for the simulation +box parameters and timestep and elapsed time. Thus it is easy to +specify parameters that change as a function of time or span +consecutive runs in a continuous fashion. For the latter, see the +start and stop keywords of the run command and the +elaplong keyword of thermo_style custom for +details. +
+For example, these commands would change the prefactor coefficient of +the pair_style soft potential from 10.0 to 30.0 in a +linear fashion over the course of a 1000-step simulation: +
+variable min equal 10.0 +variable max equal 30.0 +variable prefactor equal min+(max-min)*elapsed/1000 +fix 1 all adapt 1 pair soft a * * prefactor ++
The atom keyword enables various atom properties to be changed. The +aparam argument is the name of the parameter to change. This is the +current list of atom parameters that can be varied by this fix: +
+The avariable argument is the name of an equal-style +variable which will be evaluated each time this fix is +invoked to set the parameter to a new value. See the discussion above +describing the formulas associated with equal-style variables. The +new value is assigned to the corresponding attribute for all atoms in +the fix group. +
+For example, these commands would shrink the diameter of all granular +particles in the "center" group from 1.0 to 0.1 in a linear fashion +over the course of a 1000-step simulation: +
+variable start equal 1.0 +variable stop equal 0.1 +variable size equal start+(stop-start)*elapsed/1000 +fix 1 center adapt 10 atom diameter size ++
Restart, fix_modify, output, run start/stop, minimize info: +
+No information about this fix is written to binary restart +files. None of the fix_modify options +are relevant to this fix. No global or per-atom quantities are stored +by this fix for access by various output +commands. No parameter of this fix can be +used with the start/stop keywords of the run command. +This fix is not invoked during energy minimization. +
+Restrictions: none +
+Related commands: none +
+Default: none +
+ diff --git a/doc/fix_adapt.txt b/doc/fix_adapt.txt new file mode 100644 index 0000000000..5a26096271 --- /dev/null +++ b/doc/fix_adapt.txt @@ -0,0 +1,141 @@ +"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c + +:link(lws,http://lammps.sandia.gov) +:link(ld,Manual.html) +:link(lc,Section_commands.html#comm) + +:line + +fix adapt command :h3 + +[Syntax:] + +fix ID group-ID adapt N keyword values ... :pre +ID, group-ID are documented in "fix"_fix.html command :ulb,l +adapt = style name of this fix command :l +N = adapt simulation settings every this many timesteps :l +one or more keyword/value pairs may be appended :l +keyword = {pair} or {atom} :l + {pair} args = pstyle param I J variable + pstyle = pair style name, e.g. lj/cut + pparam = parameter to adapt over time + I,J = type pair(s) to set parameter for + pvariable = name of variable that calculates value of parameter + {atom} args = param variable + aparam = parameter to adapt over time + avariable = name of variable that calculates value of parameter :pre +:ule + +[Examples:] + +fix 1 all adapt 1 pair soft a 1 1 prefactor +fix 1 all adapt 1 pair soft a 2* 3 prefactor +fix 1 all adapt 1 pair soft a * * prefactor soft a 3 3 prefactor2 +fix 1 all adapt 10 atom diameter size :pre + +[Description:] + +Change or adapt one or more specific simulation settings over time as +a simulation runs. Pair potential and atom attribute parameters which +can be varied by this fix are discussed below. Many other fixes can +also be used to time-vary simulation parameters, e.g. the "fix deform" +command will change the simulation box size/shape and the "fix move" +command will change atom positions and velocities in prescribed +manners. + +The {pair} keyword enables various parameters of potentials defined by +the "pair_style"_pair_style.html command to be changed, if the pair +style supports it. The {pstyle} argument is the name of the pair +style. If "pair_style hybrid or hybrid/overlay"_pair_hybrid.html is +used, {pstyle} should be a sub-style name. For example, {pstyle} +could be specified as "soft" or "lubricate". The {pparam} argument is +the name of the parameter to change. This is the current list of pair +styles and parameters that can be varied by this fix. See the doc +pages for individual pair styles for the meaning of these parameters. + +"soft"_pair_soft.html, a, global, +"lubricate"_pair_lubricate.html, mu, type pairs :tb(c=3) + +Some parameters are global settings for the pair style, e.g. the +viscosity setting "mu" for "pair_style lubricate"_pair_lubricate.html. +Other parameters apply to pairs of atom types within the pair style, +e.g. the prefactor "a" for "pair_style soft"_pair_soft.html. If a +type pair parameter is specified, the {I} and {J} settings should be +specified to indicate which pair(s) to apply it to. + +Similar to the "pair_coeff command"_pair_coeff.html, I and J can be +specified in one of two ways. Explicit numeric values can be used for +each, as in the 1st example above. I <= J is required. LAMMPS sets +the coefficients for the symmetric J,I interaction to the same values. + +A wild-card asterisk can be used in place of or in conjunction with +the I,J arguments to set the coefficients for multiple pairs of atom +types. This takes the form "*" or "*n" or "n*" or "m*n". If N = the +number of atom types, then an asterisk with no numeric values means +all types from 1 to N. A leading asterisk means all types from 1 to n +(inclusive). A trailing asterisk means all types from n to N +(inclusive). A middle asterisk means all types from m to n +(inclusive). Note that only type pairs with I <= J are considered; if +asterisks imply type pairs where J < I, they are ignored. + +If a global parameter is specified, the {I} and {J} settings still +need to be specified, but are ignored. + +The {pvariable} argument is the name of an equal-style +"variable"_variable.html which will be evaluated each time this fix is +invoked to set the parameter to a new value. Equal-style variables +can specify formulas with various mathematical functions, and include +"thermo_style"_thermo_style.html command keywords for the simulation +box parameters and timestep and elapsed time. Thus it is easy to +specify parameters that change as a function of time or span +consecutive runs in a continuous fashion. For the latter, see the +{start} and {stop} keywords of the "run"_run.html command and the +{elaplong} keyword of "thermo_style custom"_thermo_style.html for +details. + +For example, these commands would change the prefactor coefficient of +the "pair_style soft"_pair_soft.html potential from 10.0 to 30.0 in a +linear fashion over the course of a 1000-step simulation: + +variable min equal 10.0 +variable max equal 30.0 +variable prefactor equal min+(max-min)*elapsed/1000 +fix 1 all adapt 1 pair soft a * * prefactor :pre + +The {atom} keyword enables various atom properties to be changed. The +{aparam} argument is the name of the parameter to change. This is the +current list of atom parameters that can be varied by this fix: + +diameter = diameter of particle :ul + +The {avariable} argument is the name of an equal-style +"variable"_variable.html which will be evaluated each time this fix is +invoked to set the parameter to a new value. See the discussion above +describing the formulas associated with equal-style variables. The +new value is assigned to the corresponding attribute for all atoms in +the fix group. + +For example, these commands would shrink the diameter of all granular +particles in the "center" group from 1.0 to 0.1 in a linear fashion +over the course of a 1000-step simulation: + +variable start equal 1.0 +variable stop equal 0.1 +variable size equal start+(stop-start)*elapsed/1000 +fix 1 center adapt 10 atom diameter size :pre + +[Restart, fix_modify, output, run start/stop, minimize info:] + +No information about this fix is written to "binary restart +files"_restart.html. None of the "fix_modify"_fix_modify.html options +are relevant to this fix. No global or per-atom quantities are stored +by this fix for access by various "output +commands"_Section_howto.html#4_15. No parameter of this fix can be +used with the {start/stop} keywords of the "run"_run.html command. +This fix is not invoked during "energy minimization"_minimize.html. + +[Restrictions:] none + +[Related commands:] none + +[Default:] none