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sjplimp 2008-03-18 23:27:40 +00:00
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commit 05308433bb
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21
doc/fix_press_berendsen.html
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@ -125,16 +125,17 @@ fmsec or psec - see the <A HREF = "units.html">units</A> command).
bulk modulus of the system (inverse of isothermal compressibility). bulk modulus of the system (inverse of isothermal compressibility).
The bulk modulus has units of pressure and is the amount of pressure The bulk modulus has units of pressure and is the amount of pressure
that would need to be applied (isotropically) to reduce the volume of that would need to be applied (isotropically) to reduce the volume of
the system by a factor of 2. The bulk modulus can be set via the the system by a factor of 2 (assuming the bulk modulus was a constant,
keyword <I>modulus</I>. The <I>Pdamp</I> parameter is effectively multiplied by independent of density, which it's not). The bulk modulus can be set
the bulk modulus, so if the pressure is relaxing faster than expected via the keyword <I>modulus</I>. The <I>Pdamp</I> parameter is effectively
or desired, increasing the bulk modulus has the same effect as multiplied by the bulk modulus, so if the pressure is relaxing faster
increasing <I>Pdamp</I>. The converse is also true. LAMMPS does not than expected or desired, increasing the bulk modulus has the same
attempt to guess a correct value of the bulk modulus; it just uses effect as increasing <I>Pdamp</I>. The converse is also true. LAMMPS does
10.0 as a default value which is about right for a Lennard-Jones not attempt to guess a correct value of the bulk modulus; it just uses
liquid, but will be way off for other materials and way too small for 10.0 as a default value which gives reasonable relaxation for a
solids. Thus you should experiment to find appropriate values of Lennard-Jones liquid, but will be way off for other materials and way
<I>Pdamp</I> and/or the <I>modulus</I> when using this fix. too small for solids. Thus you should experiment to find appropriate
values of <I>Pdamp</I> and/or the <I>modulus</I> when using this fix.
</P> </P>
<HR> <HR>

21
doc/fix_press_berendsen.txt
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@ -116,16 +116,17 @@ IMPORTANT NOTE: The relaxation time is actually also a function of the
bulk modulus of the system (inverse of isothermal compressibility). bulk modulus of the system (inverse of isothermal compressibility).
The bulk modulus has units of pressure and is the amount of pressure The bulk modulus has units of pressure and is the amount of pressure
that would need to be applied (isotropically) to reduce the volume of that would need to be applied (isotropically) to reduce the volume of
the system by a factor of 2. The bulk modulus can be set via the the system by a factor of 2 (assuming the bulk modulus was a constant,
keyword {modulus}. The {Pdamp} parameter is effectively multiplied by independent of density, which it's not). The bulk modulus can be set
the bulk modulus, so if the pressure is relaxing faster than expected via the keyword {modulus}. The {Pdamp} parameter is effectively
or desired, increasing the bulk modulus has the same effect as multiplied by the bulk modulus, so if the pressure is relaxing faster
increasing {Pdamp}. The converse is also true. LAMMPS does not than expected or desired, increasing the bulk modulus has the same
attempt to guess a correct value of the bulk modulus; it just uses effect as increasing {Pdamp}. The converse is also true. LAMMPS does
10.0 as a default value which is about right for a Lennard-Jones not attempt to guess a correct value of the bulk modulus; it just uses
liquid, but will be way off for other materials and way too small for 10.0 as a default value which gives reasonable relaxation for a
solids. Thus you should experiment to find appropriate values of Lennard-Jones liquid, but will be way off for other materials and way
{Pdamp} and/or the {modulus} when using this fix. too small for solids. Thus you should experiment to find appropriate
values of {Pdamp} and/or the {modulus} when using this fix.
:line :line