convert docs for fixes eos/cv, eos/table/rx, gcmc, grem, langevin/spin, lb/fluid

doc/src/Eqs/fix_eos-cv.tex

@@ -1,9 +0,0 @@
-\documentstyle[12pt]{article}
-\pagestyle{empty}
-\begin{document}
-
-$$
-   u_{i} = u^{mech}_{i} + u^{cond}_{i} = C_{V} \theta_{i}
-$$
-
-\end{document}

doc/src/Eqs/fix_eos_table_rx.tex

@@ -1,9 +0,0 @@
-\documentstyle[12pt]{article}
-\pagestyle{empty}
-\begin{document}
-
-\begin{eqnarray*}
-   U_{i} = \displaystyle\sum_{j=1}^{m} c_{i,j}(u_{j} + \Delta H_{f,j}) + \frac{3k_{b}T}{2} + Nk_{b}T \\ 
-\end{eqnarray*}                           
-
-\end{document}

doc/src/Eqs/fix_gcmc1.tex

@@ -1,9 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-\begin{eqnarray*}
-\mu &=&\mu^{id} + \mu^{ex}
-\end{eqnarray*}
-
-\end{document}

doc/src/Eqs/fix_gcmc2.tex

@@ -1,10 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-\begin{eqnarray*}
-\mu^{id} &=& k T \ln{\rho \Lambda^3} \\
-&=& k T \ln{\frac{\phi P \Lambda^3}{k T}} 
-\end{eqnarray*}
-
-\end{document}

doc/src/Eqs/fix_gcmc3.tex

@@ -1,9 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-\begin{eqnarray*}
-\Lambda &=& \sqrt{ \frac{h^2}{2 \pi m k T}}
-\end{eqnarray*}
-
-\end{document}

doc/src/Eqs/fix_grem.tex

@@ -1,9 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$
-  T_{eff} = \lambda + \eta (H - H_0)
-$$
-
-\end{document}

doc/src/Eqs/fix_lb_fluid_boltzmann.tex

@@ -1,14 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-\left(\partial_t + e_{i\alpha}\partial_{\alpha}\right)f_i = -\frac{1}{\tau}\left(f_i - f_i^{eq}\right) + W_i
-$$
-
-
-\end{document}
-
-
-
-

doc/src/Eqs/fix_lb_fluid_fluidforce.tex

@@ -1,14 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-{\bf F}_{j \alpha} = \gamma \left({\bf v}_n - {\bf u}_f \right) \zeta_{j\alpha}
-$$
-
-
-\end{document}
-
-
-
-

doc/src/Eqs/fix_lb_fluid_gammadefault.tex

@@ -1,14 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-\gamma = \frac{2m_um_v}{m_u+m_v}\left(\frac{1}{\Delta t_{collision}}\right)
-$$
-
-
-\end{document}
-
-
-
-

doc/src/Eqs/fix_lb_fluid_navierstokes.tex

@@ -1,16 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-\partial_t \rho + \partial_{\beta}\left(\rho u_{\beta}\right)= 0
-$$
-$$
-\partial_t\left(\rho u_{\alpha}\right) + \partial_{\beta}\left(\rho u_{\alpha} u_{\beta}\right) = \partial_{\beta}\sigma_{\alpha \beta} + F_{\alpha} + \partial_{\beta}\left(\eta_{\alpha \beta \gamma \nu}\partial_{\gamma} u_{\nu}\right)
-$$
-
-\end{document}
-
-
-
-

doc/src/Eqs/fix_lb_fluid_properties.tex

@@ -1,17 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-\rho = \displaystyle\sum\limits_{i} f_i
-$$
-$$
-\rho u_{\alpha} = \displaystyle\sum\limits_{i} f_i e_{i\alpha}
-$$
-
-
-\end{document}
-
-
-
-

doc/src/Eqs/fix_lb_fluid_stress.tex

@@ -1,14 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-\sigma_{\alpha \beta} = -P_{\alpha \beta} = -\rho a_0 \delta_{\alpha \beta}
-$$
-
-
-\end{document}
-
-
-
-

doc/src/Eqs/fix_lb_fluid_viscosity.tex

@@ -1,14 +0,0 @@
-\documentclass[12pt]{article}
-
-\begin{document}
-
-$$ 
-\eta_{\alpha \beta \gamma \nu} = \eta\left[\delta_{\alpha \gamma}\delta_{\beta \nu} + \delta_{\alpha \nu}\delta_{\beta \gamma} - \frac{2}{3}\delta_{\alpha \beta}\delta_{\gamma \nu}\right] + \Lambda \delta_{\alpha \beta}\delta_{\gamma \nu}
-$$
-
-
-\end{document}
-
-
-
-

doc/src/fix_eos_cv.rst

@@ -27,17 +27,19 @@ Description
 """""""""""
 
 Fix *eos/cv* applies a mesoparticle equation of state to relate the
-particle internal energy (u\_i) to the particle internal temperature
-(dpdTheta\_i).  The *eos/cv* mesoparticle equation of state requires
+particle internal energy (:math:`u_i`) to the particle internal temperature
+(:math:`\theta_i`).  The *eos/cv* mesoparticle equation of state requires
 the constant-volume heat capacity, and is defined as follows:
 
-.. image:: Eqs/fix_eos-cv.jpg
-   :align: center
+.. math::
 
-where Cv is the constant-volume heat capacity, u\_cond is the internal
-conductive energy, and u\_mech is the internal mechanical energy.  Note
-that alternative definitions of the mesoparticle equation of state are
-possible.
+   u_{i} = u^{mech}_{i} + u^{cond}_{i} = C_{V} \theta_{i}
+
+
+where :math:`C_V` is the constant-volume heat capacity, :math:`u^{cond}`
+is the internal conductive energy, and :math:`u^{mech}` is the internal
+mechanical energy.  Note that alternative definitions of the mesoparticle
+equation of state are possible.
 
 
 ----------

doc/src/fix_eos_table_rx.rst

@@ -40,30 +40,34 @@ Description
 
 Fix *eos/table/rx* applies a tabulated mesoparticle equation
 of state to relate the concentration-dependent particle internal
-energy (u\_i) to the particle internal temperature (dpdTheta\_i).
+energy (:math:`u_i`) to the particle internal temperature (:math:`\theta_i`).
 
-The concentration-dependent particle internal energy (u\_i) is
+The concentration-dependent particle internal energy (:math:`u_i`) is
 computed according to the following relation:
 
-.. image:: Eqs/fix_eos_table_rx.jpg
-   :align: center
+.. math::
 
-where *m* is the number of species, *c\_i,j* is the concentration of
-species *j* in particle *i*\ , *u\_j* is the internal energy of species j,
-*DeltaH\_f,j* is the heat of formation of species *j*\ , N is the number of
-molecules represented by the coarse-grained particle, kb is the
-Boltzmann constant, and T is the temperature of the system.  Additionally,
-it is possible to modify the concentration-dependent particle internal
+   U_{i} = \displaystyle\sum_{j=1}^{m} c_{i,j}(u_{j} + \Delta H_{f,j}) + \frac{3k_{b}T}{2} + Nk_{b}T \\ 
+
+
+where *m* is the number of species, :math:`c_{i,j}` is the
+concentration of species *j* in particle *i*\ , :math:`u_j` is the
+internal energy of species j, :math:`\Delta H_{f,j} is the heat of
+formation of species *j*\ , N is the number of molecules represented
+by the coarse-grained particle, :math:`k_b` is the Boltzmann constant,
+and *T* is the temperature of the system.  Additionally, it is
+possible to modify the concentration-dependent particle internal
 energy relation by adding an energy correction, temperature-dependent
-correction, and/or a molecule-dependent correction.  An energy correction can
-be specified as a constant (in energy units).  A temperature correction can be
-specified by multiplying a temperature correction coefficient by the
-internal temperature.  A molecular correction can be specified by
-by multiplying a molecule correction coefficient by the average number of
-product gas particles in the coarse-grain particle.
+correction, and/or a molecule-dependent correction.  An energy
+correction can be specified as a constant (in energy units).  A
+temperature correction can be specified by multiplying a temperature
+correction coefficient by the internal temperature.  A molecular
+correction can be specified by by multiplying a molecule correction
+coefficient by the average number of product gas particles in the
+coarse-grain particle.
 
 Fix *eos/table/rx* creates interpolation tables of length *N* from *m*
-internal energy values of each species *u\_j* listed in a file as a
+internal energy values of each species :math:`u_j` listed in a file as a
 function of internal temperature.  During a simulation, these tables
 are used to interpolate internal energy or temperature values as needed.
 The interpolation is done with the *linear* style.  For the *linear* style,
@@ -72,20 +76,21 @@ which an internal energy is computed by linear interpolation.  A secant
 solver is used to determine the internal temperature from the internal energy.
 
 The first filename specifies a file containing tabulated internal
-temperature and *m* internal energy values for each species *u\_j*.
+temperature and *m* internal energy values for each species :math:`u_j`.
 The keyword specifies a section of the file.  The format of this
 file is described below.
 
 The second filename specifies a file containing heat of formation
-*DeltaH\_f,j* for each species.
+:math:`\Delta H_{f,j}` for each species.
 
 In cases where the coarse-grain particle represents a single molecular
-species (i.e., no reactions occur and fix *rx* is not present in the input file),
-fix *eos/table/rx* can be applied in a similar manner to fix *eos/table*
-within a non-reactive DPD simulation.  In this case, the heat of formation
-filename is replaced with the heat of formation value for the single species.
-Additionally, the energy correction and temperature correction coefficients may
-also be specified as fix arguments.
+species (i.e., no reactions occur and fix *rx* is not present in the
+input file), fix *eos/table/rx* can be applied in a similar manner to
+fix *eos/table* within a non-reactive DPD simulation.  In this case,
+the heat of formation filename is replaced with the heat of formation
+value for the single species.  Additionally, the energy correction and
+temperature correction coefficients may also be specified as fix
+arguments.
 
 
 ----------

doc/src/fix_gcmc.rst

@@ -248,8 +248,10 @@ two groups: the default group "all" and the fix group
 The chemical potential is a user-specified input parameter defined
 as:
 
-.. image:: Eqs/fix_gcmc1.jpg
-   :align: center
+.. math::
+
+   \mu = \mu^{id} + \mu^{ex}
+
 
 The second term mu\_ex is the excess chemical potential due to
 energetic interactions and is formally zero for the fictitious gas
@@ -260,31 +262,35 @@ quite different.  The first term mu\_id is the ideal gas contribution
 to the chemical potential.  mu\_id can be related to the density or
 pressure of the fictitious gas reservoir by:
 
-.. image:: Eqs/fix_gcmc2.jpg
-   :align: center
+.. math::
 
-where k is Boltzman's constant,
-T is the user-specified temperature, rho is the number density,
-P is the pressure, and phi is the fugacity coefficient.
-The constant Lambda is required for dimensional consistency.
-For all unit styles except *lj* it is defined as the thermal
-de Broglie wavelength
+   \mu^{id}  = & k T \ln{\rho \Lambda^3} \\
+             = & k T \ln{\frac{\phi P \Lambda^3}{k T}} 
 
-.. image:: Eqs/fix_gcmc3.jpg
-   :align: center
 
-where h is Planck's constant, and m is the mass of the exchanged atom
-or molecule.  For unit style *lj*\ , Lambda is simply set to the
-unity. Note that prior to March 2017, lambda for unit style *lj* was
-calculated using the above formula with h set to the rather specific
+where *k* is Boltzman's constant, *T* is the user-specified
+temperature, :math:`\rho` is the number density, *P* is the pressure,
+and :math:`\phi` is the fugacity coefficient.  The constant
+:math:`\Lambda` is required for dimensional consistency.  For all unit
+styles except *lj* it is defined as the thermal de Broglie wavelength
+
+.. math::
+
+   \Lambda = \sqrt{ \frac{h^2}{2 \pi m k T}}
+
+
+where *h* is Planck's constant, and *m* is the mass of the exchanged atom
+or molecule.  For unit style *lj*\ , :math:`\Lambda` is simply set to
+unity. Note that prior to March 2017, :math:`\Lambda` for unit style *lj*
+was calculated using the above formula with *h* set to the rather specific
 value of 0.18292026.  Chemical potential under the old definition can
 be converted to an equivalent value under the new definition by
-subtracting 3kTln(Lambda\_old).
+subtracting :math:`3 k T \ln(\Lambda_{old})`.
 
 As an alternative to specifying mu directly, the ideal gas reservoir
-can be defined by its pressure P using the *pressure* keyword, in
+can be defined by its pressure *P* using the *pressure* keyword, in
 which case the user-specified chemical potential is ignored. The user
-may also specify the fugacity coefficient phi using the
+may also specify the fugacity coefficient :math:`\phi` using the
 *fugacity\_coeff* keyword, which defaults to unity.
 
 The *full\_energy* option means that the fix calculates the total
@@ -322,7 +328,7 @@ this will ensure roughly the same behavior whether or not the
 *full\_energy* option is used.
 
 Inserted atoms and molecules are assigned random velocities based on
-the specified temperature T. Because the relative velocity of all
+the specified temperature *T*. Because the relative velocity of all
 atoms in the molecule is zero, this may result in inserted molecules
 that are systematically too cold. In addition, the intramolecular
 potential energy of the inserted molecule may cause the kinetic energy

doc/src/fix_grem.rst

@@ -38,17 +38,19 @@ which uses non-Boltzmann ensembles to sample over first order phase
 transitions. The is done by defining replicas with an enthalpy
 dependent effective temperature
 
-.. image:: Eqs/fix_grem.jpg
-   :align: center
+.. math::
 
-with *eta* negative and steep enough to only intersect the
+  T_{eff} = \lambda + \eta (H - H_0)
+
+
+with :math:`\eta` negative and steep enough to only intersect the
 characteristic microcanonical temperature (Ts) of the system once,
-ensuring a unimodal enthalpy distribution in that replica. *Lambda* is
-the intercept and effects the generalized ensemble similar to how
-temperature effects a Boltzmann ensemble. *H0* is a reference
-enthalpy, and is typically set as the lowest desired sampled enthalpy.
-Further explanation can be found in our recent papers
-:ref:`(Malolepsza) <Malolepsza>`.
+ensuring a unimodal enthalpy distribution in that replica.
+:math:`\lambda` is the intercept and effects the generalized ensemble
+similar to how temperature effects a Boltzmann ensemble. :math:`H_0`
+is a reference enthalpy, and is typically set as the lowest desired
+sampled enthalpy.  Further explanation can be found in our recent
+papers :ref:`(Malolepsza) <Malolepsza>`.
 
 This fix requires a Nose-Hoover thermostat fix reference passed to the
 grem as *thermostat-ID*\ . Two distinct temperatures exist in this
@@ -59,13 +61,13 @@ algorithms can be used.
 
 The fix enforces a generalized ensemble in a single replica
 only. Typically, this ideology is combined with replica exchange with
-replicas differing by *lambda* only for simplicity, but this is not
+replicas differing by :math:`\lambda` only for simplicity, but this is not
 required. A multi-replica simulation can be run within the LAMMPS
 environment using the :doc:`temper/grem <temper_grem>` command. This
 utilizes LAMMPS partition mode and requires the number of available
 processors be on the order of the number of desired replicas. A
 100-replica simulation would require at least 100 processors (1 per
-world at minimum). If a many replicas are needed on a small number of
+world at minimum). If many replicas are needed on a small number of
 processors, multi-replica runs can be run outside of LAMMPS.  An
 example of this can be found in examples/USER/misc/grem and has no
 limit on the number of replicas per processor. However, this is very
@@ -74,13 +76,13 @@ inefficient and error prone and should be avoided if possible.
 In general, defining the generalized ensembles is unique for every
 system. When starting a many-replica simulation without any knowledge
 of the underlying microcanonical temperature, there are several tricks
-we have utilized to optimize the process.  Choosing a less-steep *eta*
-yields broader distributions, requiring fewer replicas to map the
-microcanonical temperature.  While this likely struggles from the same
-sampling problems gREM was built to avoid, it provides quick insight
-to Ts.  Initially using an evenly-spaced *lambda* distribution
-identifies regions where small changes in enthalpy lead to large
-temperature changes. Replicas are easily added where needed.
+we have utilized to optimize the process.  Choosing a less-steep
+:math:`\eta` yields broader distributions, requiring fewer replicas to
+map the microcanonical temperature.  While this likely struggles from
+the same sampling problems gREM was built to avoid, it provides quick
+insight to Ts.  Initially using an evenly-spaced :math:`\lambda`
+distribution identifies regions where small changes in enthalpy lead
+to large temperature changes. Replicas are easily added where needed.
 
 
 ----------

doc/src/fix_langevin_spin.rst

@@ -36,16 +36,19 @@ Brownian dynamics (BD).
 A random torque and a transverse dissipation are applied to each spin i according to
 the following stochastic differential equation:
 
-.. image:: Eqs/fix_langevin_spin_sLLG.jpg
-   :align: center
+.. math::
 
-with lambda the transverse damping, and eta a random vector.
+   \frac{d \vec{s}_{i}}{dt} = \frac{1}{\left(1+\lambda^2 \right)} \left( \left(
+   \vec{\omega}_{i} +\vec{\eta} \right) \times \vec{s}_{i} + \lambda\, \vec{s}_{i}
+  \times\left( \vec{\omega}_{i} \times\vec{s}_{i} \right) \right)
+
+with :math:`\lambda` the transverse damping, and :math:`\eta` a random vector.
 This equation is referred to as the stochastic Landau-Lifshitz-Gilbert (sLLG)
 equation.
 
-The components of eta are drawn from a Gaussian probability law. Their amplitude
-is defined as a proportion of the temperature of the external thermostat T (in K
-in metal units).
+The components of :math:`\eta` are drawn from a Gaussian probability
+law. Their amplitude is defined as a proportion of the temperature of
+the external thermostat T (in K in metal units).
 
 More details about this implementation are reported in :ref:`(Tranchida) <Tranchida2>`.
 

doc/src/fix_lb_fluid.rst

@@ -69,33 +69,42 @@ dependent force to the fluid.
 The lattice-Boltzmann algorithm solves for the fluid motion governed by
 the Navier Stokes equations,
 
-.. image:: Eqs/fix_lb_fluid_navierstokes.jpg
-   :align: center
+.. math::
+   
+   \partial_t \rho + \partial_{\beta}\left(\rho u_{\beta}\right)= & 0 \\
+   \partial_t\left(\rho u_{\alpha}\right) + \partial_{\beta}\left(\rho u_{\alpha} u_{\beta}\right) = & \partial_{\beta}\sigma_{\alpha \beta} + F_{\alpha} + \partial_{\beta}\left(\eta_{\alpha \beta \gamma \nu}\partial_{\gamma} u_{\nu}\right)
+
 
 with,
 
-.. image:: Eqs/fix_lb_fluid_viscosity.jpg
-   :align: center
+.. math::
 
-where rho is the fluid density, u is the local fluid velocity, sigma
-is the stress tensor, F is a local external force, and eta and Lambda
-are the shear and bulk viscosities respectively.  Here, we have
-implemented
+   \eta_{\alpha \beta \gamma \nu} = \eta\left[\delta_{\alpha \gamma}\delta_{\beta \nu} + \delta_{\alpha \nu}\delta_{\beta \gamma} - \frac{2}{3}\delta_{\alpha \beta}\delta_{\gamma \nu}\right] + \Lambda \delta_{\alpha \beta}\delta_{\gamma \nu}
 
-.. image:: Eqs/fix_lb_fluid_stress.jpg
-   :align: center
 
-with a\_0 set to 1/3 (dx/dt)\^2 by default.
+where :math:`\rho` is the fluid density, *u* is the local
+fluid velocity, :math:`\sigma` is the stress tensor, *F* is a local external
+force, and :math:`\eta` and :math:`\Lambda` are the shear and bulk viscosities
+respectively.  Here, we have implemented
+
+.. math::
+
+   \sigma_{\alpha \beta} = -P_{\alpha \beta} = -\rho a_0 \delta_{\alpha \beta}
+
+
+with :math:`a_0` set to :math:`\frac{1}{3} \frac{dx}{dt}^2` by default.
 
 The algorithm involves tracking the time evolution of a set of partial
 distribution functions which evolve according to a velocity
 discretized version of the Boltzmann equation,
 
-.. image:: Eqs/fix_lb_fluid_boltzmann.jpg
-   :align: center
+.. math::
+
+   \left(\partial_t + e_{i\alpha}\partial_{\alpha}\right)f_i = -\frac{1}{\tau}\left(f_i - f_i^{eq}\right) + W_i
+
 
 where the first term on the right hand side represents a single time
-relaxation towards the equilibrium distribution function, and tau is a
+relaxation towards the equilibrium distribution function, and :math:`\tau` is a
 parameter physically related to the viscosity.  On a technical note,
 we have implemented a 15 velocity model (D3Q15) as default; however,
 the user can switch to a 19 velocity model (D3Q19) through the use of
@@ -108,8 +117,10 @@ finite difference LB integrator is used.  If *LBtype* is set equal to
 Physical variables are then defined in terms of moments of the distribution
 functions,
 
-.. image:: Eqs/fix_lb_fluid_properties.jpg
-   :align: center
+.. math::
+
+   \rho = & \displaystyle\sum\limits_{i} f_i \\
+   \rho u_{\alpha} = \displaystyle\sum\limits_{i} f_i e_{i\alpha}
 
 Full details of the lattice-Boltzmann algorithm used can be found in
 :ref:`Mackay et al. <fluid-Mackay>`.
@@ -119,12 +130,15 @@ through a velocity dependent force.  The contribution to the fluid
 force on a given lattice mesh site j due to MD particle alpha is
 calculated as:
 
-.. image:: Eqs/fix_lb_fluid_fluidforce.jpg
-   :align: center
+.. math::
 
-where v\_n is the velocity of the MD particle, u\_f is the fluid
+   {\bf F}_{j \alpha} = \gamma \left({\bf v}_n - {\bf u}_f \right) \zeta_{j\alpha}
+
+
+where :math:`\mathbf{v}_n` is the velocity of the MD particle,
+:math:`\mathbf{u}_f` is the fluid
 velocity interpolated to the particle location, and gamma is the force
-coupling constant.  Zeta is a weight assigned to the grid point,
+coupling constant.  :math:`\zeta` is a weight assigned to the grid point,
 obtained by distributing the particle to the nearest lattice sites.
 For this, the user has the choice between a trilinear stencil, which
 provides a support of 8 lattice sites, or the immersed boundary method
@@ -135,20 +149,25 @@ to walls, due to its smaller support.  Therefore, by default, the
 Peskin stencil is used; however the user may switch to the trilinear
 stencil by specifying the keyword, *trilinear*\ .
 
-By default, the force coupling constant, gamma, is calculated according to
+By default, the force coupling constant, :math:`\gamma`, is calculated
+according to
 
-.. image:: Eqs/fix_lb_fluid_gammadefault.jpg
-   :align: center
+.. math::
 
-Here, m\_v is the mass of the MD particle, m\_u is a representative
-fluid mass at the particle location, and dt\_collision is a collision
-time, chosen such that tau/dt\_collision = 1 (see :ref:`Mackay and Denniston <Mackay2>` for full details).  In order to calculate m\_u, the
-fluid density is interpolated to the MD particle location, and
-multiplied by a volume, node\_area\*dx\_lb, where node\_area represents
-the portion of the surface area of the composite object associated
-with a given MD particle.  By default, node\_area is set equal to
-dx\_lb\*dx\_lb; however specific values for given atom types can be set
-using the *setArea* keyword.
+   \gamma = \frac{2m_um_v}{m_u+m_v}\left(\frac{1}{\Delta t_{collision}}\right)
+
+
+Here, :math:`m_v` is the mass of the MD particle, :math:`m_u` is a
+representative fluid mass at the particle location, and :math:`\Delta
+t_{collision}` is a collision time, chosen such that
+:math:`\frac{\tau}{\Delta t_{collision}} = 1` (see :ref:`Mackay and
+Denniston <Mackay2>` for full details).  In order to calculate :math:`m_u`,
+the fluid density is interpolated to the MD particle location, and
+multiplied by a volume, node\_area\*dx\_lb, where node\_area
+represents the portion of the surface area of the composite object
+associated with a given MD particle.  By default, node\_area is set
+equal to dx\_lb\*dx\_lb; however specific values for given atom types
+can be set using the *setArea* keyword.
 
 The user also has the option of specifying their own value for the
 force coupling constant, for all the MD particles associated with the
@@ -364,8 +383,10 @@ Default
 
 By default, the force coupling constant is set according to
 
-.. image:: Eqs/fix_lb_fluid_gammadefault.jpg
-   :align: center
+.. math::
+
+   \gamma = \frac{2m_um_v}{m_u+m_v}\left(\frac{1}{\Delta t_{collision}}\right)
+
 
 and an area of dx\_lb\^2 per node, used to calculate the fluid mass at
 the particle node location, is assumed.