mirror of https://github.com/lammps/lammps.git
git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@4279 f3b2605a-c512-4ea7-a41b-209d697bcdaa
This commit is contained in:
sjplimp
parent
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|
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@ -43,51 +43,53 @@ fix 2 all msst z 50.0 q 1.0e4 mu 1.0e4 v0 4.3419e+03 p0 3.7797e+03 e0 -9.72360e
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>This command performs the Multi-Scale Shock Technique (MSST) integration
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to update positions and velocities each timestep to mimic a compressive shock
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wave passing over the system. See <A HREF = "#Reed">(Reed)</A> for a detailed description of this method.
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The MSST varies the cell volume and temperature in such a
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way as to restrain the system to the shock Hugoniot and the Rayleigh
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line. These restraints correspond to the macroscopic conservation laws
|
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dictated by a shock front. <I>shockvel</I> determines the steady shock
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velocity that will be simulated.
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<P>This command performs the Multi-Scale Shock Technique (MSST)
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integration to update positions and velocities each timestep to mimic
|
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a compressive shock wave passing over the system. See <A HREF = "#Reed">(Reed)</A>
|
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for a detailed description of this method. The MSST varies the cell
|
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volume and temperature in such a way as to restrain the system to the
|
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shock Hugoniot and the Rayleigh line. These restraints correspond to
|
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the macroscopic conservation laws dictated by a shock
|
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front. <I>shockvel</I> determines the steady shock velocity that will be
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simulated.
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</P>
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<P>To perform a simulation, choose a value of <I>q</I> that provides volume compression
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on the timescale of 100 fs to 1 ps. If the volume is not compressing, either
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the shock speed is chosen to be below the material sound speed or <I>p0</I> has been
|
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chosen inaccurately. Volume compression at the start can
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be sped up by using a non-zero value of <I>tscale</I>. Use the smallest value of
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<I>tscale</I> that results in compression.
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<P>To perform a simulation, choose a value of <I>q</I> that provides volume
|
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compression on the timescale of 100 fs to 1 ps. If the volume is not
|
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compressing, either the shock speed is chosen to be below the material
|
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sound speed or <I>p0</I> has been chosen inaccurately. Volume compression
|
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at the start can be sped up by using a non-zero value of <I>tscale</I>. Use
|
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the smallest value of <I>tscale</I> that results in compression.
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</P>
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<P>Under some special high-symmetry conditions, the pressure (volume) and/or temperature
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of the system may oscillate for many cycles even with an appropriate
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choice of mass-like parameter <I>q</I>. Such oscillations have physical
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significance in some cases. The optional <I>mu</I> keyword adds an artificial
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viscosity that helps break the system symmetry
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to equilibrate to the shock Hugoniot and Rayleigh line more rapidly in such cases.
|
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<P>Under some special high-symmetry conditions, the pressure (volume)
|
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and/or temperature of the system may oscillate for many cycles even
|
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with an appropriate choice of mass-like parameter <I>q</I>. Such
|
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oscillations have physical significance in some cases. The optional
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<I>mu</I> keyword adds an artificial viscosity that helps break the system
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symmetry to equilibrate to the shock Hugoniot and Rayleigh line more
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rapidly in such cases.
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</P>
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<P><I>tscale</I> is a factor between 0 and 1 that determines
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what fraction of thermal kinetic energy is converted to compressive strain
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kinetic energy at the start of the simulation. Setting this parameter to a
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non-zero value may assist in compression at the start of simulations where it
|
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is slow to occur.
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<P><I>tscale</I> is a factor between 0 and 1 that determines what fraction of
|
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thermal kinetic energy is converted to compressive strain kinetic
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energy at the start of the simulation. Setting this parameter to a
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non-zero value may assist in compression at the start of simulations
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where it is slow to occur.
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</P>
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<P>If keywords <I>e0</I>, <I>p0</I>,or <I>v0</I> are not supplied, these quantities will be calculated
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on the first step, after the energy specified by <I>tscale</I> is removed.
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The value of <I>e0</I> is not used in the dynamical equations,
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but is used in calculating the deviation from the Hugoniot.
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<P>If keywords <I>e0</I>, <I>p0</I>,or <I>v0</I> are not supplied, these quantities will
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be calculated on the first step, after the energy specified by
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<I>tscale</I> is removed. The value of <I>e0</I> is not used in the dynamical
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equations, but is used in calculating the deviation from the Hugoniot.
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</P>
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<P>Values of shockvel less than a critical value determined by the material
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response will not have compressive solutions. This will be reflected in
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lack of significant change of the volume in the MSST.
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<P>Values of shockvel less than a critical value determined by the
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material response will not have compressive solutions. This will be
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reflected in lack of significant change of the volume in the MSST.
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</P>
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<P>For all pressure styles, the simulation box stays orthogonal in shape.
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Parrinello-Rahman boundary conditions (tilted box) are supported by LAMMPS,
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but are not implemented for MSST.
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Parrinello-Rahman boundary conditions (tilted box) are supported by
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LAMMPS, but are not implemented for MSST.
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</P>
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<P>This fix computes a temperature and pressure each timestep. To do this,
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the fix creates its own computes of style "temp" and "pressure", as if
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these commands had been issued:
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<P>This fix computes a temperature and pressure each timestep. To do
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this, the fix creates its own computes of style "temp" and "pressure",
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as if these commands had been issued:
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</P>
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<PRE>compute fix-ID_temp group-ID temp
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compute fix-ID_press group-ID pressure fix-ID_temp
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@ -95,26 +97,26 @@ compute fix-ID_press group-ID pressure fix-ID_temp
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<P>See the <A HREF = "compute_temp.html">compute temp</A> and <A HREF = "compute_pressure.html">compute
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pressure</A> commands for details. Note that the
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IDs of the new computes are the fix-ID + underscore + "temp" or fix_ID
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+ underscore + "press". The group for
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the new computes is "all".
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+ underscore + "press". The group for the new computes is "all".
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</P>
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<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
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</P>
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<P>This fix writes the state of all internal
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variables to <A HREF = "restart.html">binary restart files</A>. See the
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<A HREF = "read_restart.html">read_restart</A> command for info on how to re-specify
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a fix in an input script that reads a restart file, so that the
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operation of the fix continues in an uninterrupted fashion.
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<P>This fix writes the state of all internal variables to <A HREF = "restart.html">binary restart
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files</A>. See the <A HREF = "read_restart.html">read_restart</A> command
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for info on how to re-specify a fix in an input script that reads a
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restart file, so that the operation of the fix continues in an
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uninterrupted fashion.
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</P>
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<P>The progress of the MSST can be monitored by printing the global scalar and
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global vector quantities computed by the fix.
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<P>The progress of the MSST can be monitored by printing the global
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scalar and global vector quantities computed by the fix.
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</P>
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<P>The scalar is the cumulative energy change due to the fix. This is also the energy
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added to the potential energy by the <A HREF = "fix_modify.html">fix_modify</A> <I>energy</I> command.
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With this command, the thermo keyword
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<I>etotal</I> prints the conserved quantity of the MSST dynamic equations. This can be
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used to test if the MD timestep is sufficiently small for accurate integration
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of the dynamic equations. See also <A HREF = "thermo_style.html">thermo_style</A> command.
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<P>The scalar is the cumulative energy change due to the fix. This is
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also the energy added to the potential energy by the
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<A HREF = "fix_modify.html">fix_modify</A> <I>energy</I> command. With this command, the
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thermo keyword <I>etotal</I> prints the conserved quantity of the MSST
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dynamic equations. This can be used to test if the MD timestep is
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sufficiently small for accurate integration of the dynamic
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equations. See also <A HREF = "thermo_style.html">thermo_style</A> command.
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</P>
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<P>The global vector contains four values in this order:
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</P>
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@ -125,20 +127,20 @@ of the dynamic equations. See also <A HREF = "thermo_style.html">thermo_style</A
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<LI><I>lagrangian_speed</I> is the laboratory-frame Lagrangian speed (particle velocity) of the computational cell (velocity units).
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<LI><I>lagrangian_position</I> is the computational cell position in the reference frame moving at the shock speed. This is usually a good estimate of distance of the computational cell behind the shock front.
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</OL>
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<P>To print these quantities to the log file with descriptive column headers, the
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following LAMMPS commands are suggested:
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<P>To print these quantities to the log file with descriptive column
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headers, the following LAMMPS commands are suggested:
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</P>
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<PRE>fix msst all msst z
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fix_modify msst energy yes
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<PRE>fix msst all msst z
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fix_modify msst energy yes
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variable dhug equal f_msst[1]
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variable dray equal f_msst[2]
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variable lgr_vel equal f_msst[3]
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variable lgr_pos equal f_msst[4]
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thermo_style custom step temp ke pe lz pzz etotal v_dhug v_dray v_lgr_vel v_lgr_pos f_msst
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thermo_style custom step temp ke pe lz pzz etotal v_dhug v_dray v_lgr_vel v_lgr_pos f_msst
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</PRE>
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<P>These fixes compute a global scalar and a global vector of 4 quantities,
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which can be accessed by various <A HREF = "Section_howto.html#4_15">output commands</A>.
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The scalar values calculated by
|
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<P>These fixes compute a global scalar and a global vector of 4
|
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quantities, which can be accessed by various <A HREF = "Section_howto.html#4_15">output
|
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commands</A>. The scalar values calculated by
|
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this fix are "extensive"; the vector values are "intensive".
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</P>
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<P><B>Restrictions:</B>
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@ -147,8 +149,9 @@ this fix are "extensive"; the vector values are "intensive".
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LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info.
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</P>
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<P>All cell dimensions must be periodic. This fix can not be used with a triclinic cell.
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The MSST fix has been tested only for the group-ID all.
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<P>All cell dimensions must be periodic. This fix can not be used with a
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triclinic cell. The MSST fix has been tested only for the group-ID
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all.
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</P>
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<P><B>Related commands:</B>
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</P>
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@ -156,7 +159,7 @@ The MSST fix has been tested only for the group-ID all.
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</P>
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<P><B>Default:</B>
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</P>
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<P>The keyword defaults are q = 10, mu = 0, tscale = 0.01. p0, v0, and e0
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<P>The keyword defaults are q = 10, mu = 0, tscale = 0.01. p0, v0, and e0
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are calculated on the first step.
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</P>
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<HR>
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|
|
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129
doc/fix_msst.txt
129
doc/fix_msst.txt
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@ -33,51 +33,53 @@ fix 2 all msst z 50.0 q 1.0e4 mu 1.0e4 v0 4.3419e+03 p0 3.7797e+03 e0 -9.72360e
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|||
|
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[Description:]
|
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|
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This command performs the Multi-Scale Shock Technique (MSST) integration
|
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to update positions and velocities each timestep to mimic a compressive shock
|
||||
wave passing over the system. See "(Reed)"_#Reed for a detailed description of this method.
|
||||
The MSST varies the cell volume and temperature in such a
|
||||
way as to restrain the system to the shock Hugoniot and the Rayleigh
|
||||
line. These restraints correspond to the macroscopic conservation laws
|
||||
dictated by a shock front. {shockvel} determines the steady shock
|
||||
velocity that will be simulated.
|
||||
This command performs the Multi-Scale Shock Technique (MSST)
|
||||
integration to update positions and velocities each timestep to mimic
|
||||
a compressive shock wave passing over the system. See "(Reed)"_#Reed
|
||||
for a detailed description of this method. The MSST varies the cell
|
||||
volume and temperature in such a way as to restrain the system to the
|
||||
shock Hugoniot and the Rayleigh line. These restraints correspond to
|
||||
the macroscopic conservation laws dictated by a shock
|
||||
front. {shockvel} determines the steady shock velocity that will be
|
||||
simulated.
|
||||
|
||||
To perform a simulation, choose a value of {q} that provides volume compression
|
||||
on the timescale of 100 fs to 1 ps. If the volume is not compressing, either
|
||||
the shock speed is chosen to be below the material sound speed or {p0} has been
|
||||
chosen inaccurately. Volume compression at the start can
|
||||
be sped up by using a non-zero value of {tscale}. Use the smallest value of
|
||||
{tscale} that results in compression.
|
||||
To perform a simulation, choose a value of {q} that provides volume
|
||||
compression on the timescale of 100 fs to 1 ps. If the volume is not
|
||||
compressing, either the shock speed is chosen to be below the material
|
||||
sound speed or {p0} has been chosen inaccurately. Volume compression
|
||||
at the start can be sped up by using a non-zero value of {tscale}. Use
|
||||
the smallest value of {tscale} that results in compression.
|
||||
|
||||
Under some special high-symmetry conditions, the pressure (volume) and/or temperature
|
||||
of the system may oscillate for many cycles even with an appropriate
|
||||
choice of mass-like parameter {q}. Such oscillations have physical
|
||||
significance in some cases. The optional {mu} keyword adds an artificial
|
||||
viscosity that helps break the system symmetry
|
||||
to equilibrate to the shock Hugoniot and Rayleigh line more rapidly in such cases.
|
||||
Under some special high-symmetry conditions, the pressure (volume)
|
||||
and/or temperature of the system may oscillate for many cycles even
|
||||
with an appropriate choice of mass-like parameter {q}. Such
|
||||
oscillations have physical significance in some cases. The optional
|
||||
{mu} keyword adds an artificial viscosity that helps break the system
|
||||
symmetry to equilibrate to the shock Hugoniot and Rayleigh line more
|
||||
rapidly in such cases.
|
||||
|
||||
{tscale} is a factor between 0 and 1 that determines
|
||||
what fraction of thermal kinetic energy is converted to compressive strain
|
||||
kinetic energy at the start of the simulation. Setting this parameter to a
|
||||
non-zero value may assist in compression at the start of simulations where it
|
||||
is slow to occur.
|
||||
{tscale} is a factor between 0 and 1 that determines what fraction of
|
||||
thermal kinetic energy is converted to compressive strain kinetic
|
||||
energy at the start of the simulation. Setting this parameter to a
|
||||
non-zero value may assist in compression at the start of simulations
|
||||
where it is slow to occur.
|
||||
|
||||
If keywords {e0}, {p0},or {v0} are not supplied, these quantities will be calculated
|
||||
on the first step, after the energy specified by {tscale} is removed.
|
||||
The value of {e0} is not used in the dynamical equations,
|
||||
but is used in calculating the deviation from the Hugoniot.
|
||||
If keywords {e0}, {p0},or {v0} are not supplied, these quantities will
|
||||
be calculated on the first step, after the energy specified by
|
||||
{tscale} is removed. The value of {e0} is not used in the dynamical
|
||||
equations, but is used in calculating the deviation from the Hugoniot.
|
||||
|
||||
Values of shockvel less than a critical value determined by the material
|
||||
response will not have compressive solutions. This will be reflected in
|
||||
lack of significant change of the volume in the MSST.
|
||||
Values of shockvel less than a critical value determined by the
|
||||
material response will not have compressive solutions. This will be
|
||||
reflected in lack of significant change of the volume in the MSST.
|
||||
|
||||
For all pressure styles, the simulation box stays orthogonal in shape.
|
||||
Parrinello-Rahman boundary conditions (tilted box) are supported by LAMMPS,
|
||||
but are not implemented for MSST.
|
||||
Parrinello-Rahman boundary conditions (tilted box) are supported by
|
||||
LAMMPS, but are not implemented for MSST.
|
||||
|
||||
This fix computes a temperature and pressure each timestep. To do this,
|
||||
the fix creates its own computes of style "temp" and "pressure", as if
|
||||
these commands had been issued:
|
||||
This fix computes a temperature and pressure each timestep. To do
|
||||
this, the fix creates its own computes of style "temp" and "pressure",
|
||||
as if these commands had been issued:
|
||||
|
||||
compute fix-ID_temp group-ID temp
|
||||
compute fix-ID_press group-ID pressure fix-ID_temp :pre
|
||||
|
|
@ -85,26 +87,26 @@ compute fix-ID_press group-ID pressure fix-ID_temp :pre
|
|||
See the "compute temp"_compute_temp.html and "compute
|
||||
pressure"_compute_pressure.html commands for details. Note that the
|
||||
IDs of the new computes are the fix-ID + underscore + "temp" or fix_ID
|
||||
+ underscore + "press". The group for
|
||||
the new computes is "all".
|
||||
+ underscore + "press". The group for the new computes is "all".
|
||||
|
||||
[Restart, fix_modify, output, run start/stop, minimize info:]
|
||||
|
||||
This fix writes the state of all internal
|
||||
variables to "binary restart files"_restart.html. See the
|
||||
"read_restart"_read_restart.html command for info on how to re-specify
|
||||
a fix in an input script that reads a restart file, so that the
|
||||
operation of the fix continues in an uninterrupted fashion.
|
||||
This fix writes the state of all internal variables to "binary restart
|
||||
files"_restart.html. See the "read_restart"_read_restart.html command
|
||||
for info on how to re-specify a fix in an input script that reads a
|
||||
restart file, so that the operation of the fix continues in an
|
||||
uninterrupted fashion.
|
||||
|
||||
The progress of the MSST can be monitored by printing the global scalar and
|
||||
global vector quantities computed by the fix.
|
||||
The progress of the MSST can be monitored by printing the global
|
||||
scalar and global vector quantities computed by the fix.
|
||||
|
||||
The scalar is the cumulative energy change due to the fix. This is also the energy
|
||||
added to the potential energy by the "fix_modify"_fix_modify.html {energy} command.
|
||||
With this command, the thermo keyword
|
||||
{etotal} prints the conserved quantity of the MSST dynamic equations. This can be
|
||||
used to test if the MD timestep is sufficiently small for accurate integration
|
||||
of the dynamic equations. See also "thermo_style"_thermo_style.html command.
|
||||
The scalar is the cumulative energy change due to the fix. This is
|
||||
also the energy added to the potential energy by the
|
||||
"fix_modify"_fix_modify.html {energy} command. With this command, the
|
||||
thermo keyword {etotal} prints the conserved quantity of the MSST
|
||||
dynamic equations. This can be used to test if the MD timestep is
|
||||
sufficiently small for accurate integration of the dynamic
|
||||
equations. See also "thermo_style"_thermo_style.html command.
|
||||
|
||||
The global vector contains four values in this order:
|
||||
|
||||
|
|
@ -115,20 +117,20 @@ The global vector contains four values in this order:
|
|||
{lagrangian_speed} is the laboratory-frame Lagrangian speed (particle velocity) of the computational cell (velocity units).
|
||||
{lagrangian_position} is the computational cell position in the reference frame moving at the shock speed. This is usually a good estimate of distance of the computational cell behind the shock front. :ol
|
||||
|
||||
To print these quantities to the log file with descriptive column headers, the
|
||||
following LAMMPS commands are suggested:
|
||||
To print these quantities to the log file with descriptive column
|
||||
headers, the following LAMMPS commands are suggested:
|
||||
|
||||
fix msst all msst z
|
||||
fix_modify msst energy yes
|
||||
fix msst all msst z
|
||||
fix_modify msst energy yes
|
||||
variable dhug equal f_msst\[1\]
|
||||
variable dray equal f_msst\[2\]
|
||||
variable lgr_vel equal f_msst\[3\]
|
||||
variable lgr_pos equal f_msst\[4\]
|
||||
thermo_style custom step temp ke pe lz pzz etotal v_dhug v_dray v_lgr_vel v_lgr_pos f_msst :pre
|
||||
thermo_style custom step temp ke pe lz pzz etotal v_dhug v_dray v_lgr_vel v_lgr_pos f_msst :pre
|
||||
|
||||
These fixes compute a global scalar and a global vector of 4 quantities,
|
||||
which can be accessed by various "output commands"_Section_howto.html#4_15.
|
||||
The scalar values calculated by
|
||||
These fixes compute a global scalar and a global vector of 4
|
||||
quantities, which can be accessed by various "output
|
||||
commands"_Section_howto.html#4_15. The scalar values calculated by
|
||||
this fix are "extensive"; the vector values are "intensive".
|
||||
|
||||
[Restrictions:]
|
||||
|
|
@ -137,8 +139,9 @@ This fix style is part of the "shock" package. It is only enabled if
|
|||
LAMMPS was built with that package. See the "Making
|
||||
LAMMPS"_Section_start.html#2_3 section for more info.
|
||||
|
||||
All cell dimensions must be periodic. This fix can not be used with a triclinic cell.
|
||||
The MSST fix has been tested only for the group-ID all.
|
||||
All cell dimensions must be periodic. This fix can not be used with a
|
||||
triclinic cell. The MSST fix has been tested only for the group-ID
|
||||
all.
|
||||
|
||||
[Related commands:]
|
||||
|
||||
|
|
@ -146,7 +149,7 @@ The MSST fix has been tested only for the group-ID all.
|
|||
|
||||
[Default:]
|
||||
|
||||
The keyword defaults are q = 10, mu = 0, tscale = 0.01. p0, v0, and e0
|
||||
The keyword defaults are q = 10, mu = 0, tscale = 0.01. p0, v0, and e0
|
||||
are calculated on the first step.
|
||||
|
||||
:line
|
||||
|
|
|
|||
Loading…
Reference in New Issue