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Added GJF Langevin method 

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@10046 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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athomps 2013-06-06 18:11:00 +00:00
parent fe71627776
commit 51814ba9bd
2 changed files with 43 additions and 4 deletions
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24
doc/fix_langevin.html
View File

@ -34,6 +34,9 @@
<PRE> <I>angmom</I> value = <I>no</I> or scale
<I>no</I> = do not thermostat rotational degrees of freedom via the angular momentum
factor = do thermostat rotational degrees of freedom via the angular momentum and apply numeric factor as discussed below
<I>gjf</I> value = <I>no</I> or <I>yes</I>
<I>no</I> = use standard formulation
<I>yes</I> = use Gronbech-Jensen/Farago formulation
<I>omega</I> value = <I>no</I> or <I>yes</I>
<I>no</I> = do not thermostat rotational degrees of freedom via the angular velocity
<I>yes</I> = do thermostat rotational degrees of freedom via the angular velocity
@ -235,6 +238,19 @@ to zero by subtracting off an equal part of it from each atom in the
group. As a result, the center-of-mass of a system with zero initial
momentum will not drift over time.
</P>
<P>The keyword <I>gjf</I> can be used to run the
<A HREF = "#Gronbech-Jensen">Gronbech-Jensen/Farago </A>
time-discretization of the Langevin model. The effective random force
is composed of
the average of two random forces representing half-contributions from
the previous and current time intervals. This discretization has been shown
to be consistent with the underlying physical model of Langevin dynamics
and produces the correct statistical distribution of energy for large
timesteps, up to the numerical stability limit. A typical simulation
with flexible hydrogen-carbon covalent bonds
can be run with a timestep of 3 fs, instead of 1 fs with the
standard Langevin method.
</P>
<HR>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
@ -281,7 +297,7 @@ dpd/tstat</A>
<P><B>Default:</B>
</P>
<P>The option defaults are angmom = no, omega = no, scale = 1.0 for all
types, tally = no, zero = no.
types, tally = no, zero = no, gjf = no.
</P>
<HR>
@ -291,6 +307,10 @@ types, tally = no, zero = no.
</P>
<A NAME = "Schneider"></A>
<P><B>(Schneider)</B> Schneider and Stoll, Phys Rev B, 17, 1302 (1978).
<P><B>(Schneider)</B> Schneider and Stoll, Phys Rev B, 17, 1302 (1978).
</P>
<A NAME = "Gronbech-Jensen"></A>
<P><B>(Gronbech-Jensen)</B> Gronbech-Jensen, Hayre, and Farago, arXiv:1303.7011.v2; Gronbech-Jensen and Farago, Mol. Phys. 111 (2013);
</P>
</HTML>

23
doc/fix_langevin.txt
View File

@ -23,6 +23,9 @@ keyword = {angmom} or {omega} or {scale} or {tally} or {zero} :l
{angmom} value = {no} or scale
{no} = do not thermostat rotational degrees of freedom via the angular momentum
factor = do thermostat rotational degrees of freedom via the angular momentum and apply numeric factor as discussed below
{gjf} value = {no} or {yes}
{no} = use standard formulation
{yes} = use Gronbech-Jensen/Farago formulation
{omega} value = {no} or {yes}
{no} = do not thermostat rotational degrees of freedom via the angular velocity
{yes} = do thermostat rotational degrees of freedom via the angular velocity
@ -223,6 +226,19 @@ to zero by subtracting off an equal part of it from each atom in the
group. As a result, the center-of-mass of a system with zero initial
momentum will not drift over time.
The keyword {gjf} can be used to run the
"Gronbech-Jensen/Farago "_#Gronbech-Jensen
time-discretization of the Langevin model. The effective random force
is composed of
the average of two random forces representing half-contributions from
the previous and current time intervals. This discretization has been shown
to be consistent with the underlying physical model of Langevin dynamics
and produces the correct statistical distribution of energy for large
timesteps, up to the numerical stability limit. A typical simulation
with flexible hydrogen-carbon covalent bonds
can be run with a timestep of 3 fs, instead of 1 fs with the
standard Langevin method.
:line
[Restart, fix_modify, output, run start/stop, minimize info:]
@ -269,7 +285,7 @@ dpd/tstat"_pair_dpd.html
[Default:]
The option defaults are angmom = no, omega = no, scale = 1.0 for all
types, tally = no, zero = no.
types, tally = no, zero = no, gjf = no.
:line
@ -277,4 +293,7 @@ types, tally = no, zero = no.
[(Dunweg)] Dunweg and Paul, Int J of Modern Physics C, 2, 817-27 (1991).
:link(Schneider)
[(Schneider)] Schneider and Stoll, Phys Rev B, 17, 1302 (1978).
[(Schneider)] Schneider and Stoll, Phys Rev B, 17, 1302 (1978).
:link(Gronbech-Jensen)
[(Gronbech-Jensen)] Gronbech-Jensen, Hayre, and Farago, arXiv:1303.7011.v2; Gronbech-Jensen and Farago, Mol. Phys. 111 (2013);