convert pair style bop to class2

This commit is contained in:
Axel Kohlmeyer
2020-02-24 16:43:40 -05:00
parent 3aa6f39425
commit 351bca4ccb
18 changed files with 111 additions and 152 deletions

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\documentclass[12pt]{article}
\begin{document}
$$
E = \frac{1}{2} \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \phi_{ij} \left( r_{ij} \right) - \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \beta_{\sigma,ij} \left( r_{ij} \right) \cdot \Theta_{\sigma,ij} - \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \beta_{\pi,ij} \left( r_{ij} \right) \cdot \Theta_{\pi,ij} + U_{prom}
$$
\end{document}

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\documentstyle[12pt]{article}
\begin{document}
$$
E = A \exp \left(\frac{\sigma - r}{\rho} \right) -
\frac{C}{r^6} + \frac{D}{r^8} \qquad r < r_c
$$
\end{document}

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\documentclass[12pt]{article}
\begin{document}
$$
E = A e^{-r / \rho} - \frac{C}{r^6} \qquad r < r_c
$$
\end{document}

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\documentclass[12pt]{article}
\begin{document}
\pagestyle{empty}
\begin{eqnarray*}
E = A e^{-\kappa r} - \frac{C}{r^6} \cdot \frac{1}{1 + D r^{14}} \qquad r < r_c \\
\end{eqnarray*}
\end{document}

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\documentclass[12pt]{article}
\begin{document}
\begin{eqnarray*}
E & = & LJ(r) \qquad \qquad \qquad r < r_{\rm in} \\
& = & S(r) * LJ(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
& = & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
E & = & C(r) \qquad \qquad \qquad r < r_{\rm in} \\
& = & S(r) * C(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
& = & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
LJ(r) & = & 4 \epsilon \left[ \left(\frac{\sigma}{r}\right)^{12} -
\left(\frac{\sigma}{r}\right)^6 \right] \\
C(r) & = & \frac{C q_i q_j}{ \epsilon r} \\
S(r) & = & \frac{ \left[r_{\rm out}^2 - r^2\right]^2
\left[r_{\rm out}^2 + 2r^2 - 3{r_{\rm in}^2}\right]}
{ \left[r_{\rm out}^2 - {r_{\rm in}}^2\right]^3 }
\end{eqnarray*}
\end{document}

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\documentstyle[12pt]{article}
\begin{document}
$$
E = \epsilon \left[ 2 \left(\frac{\sigma}{r}\right)^9 -
3 \left(\frac{\sigma}{r}\right)^6 \right]
\qquad r < r_c
$$
\end{document}

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@ -36,7 +36,7 @@ Description
"""""""""""
The *bop* pair style computes Bond-Order Potentials (BOP) based on
quantum mechanical theory incorporating both sigma and pi bonding.
quantum mechanical theory incorporating both :math:`\sigma` and :math:`\pi` bonding.
By analytically deriving the BOP from quantum mechanical theory its
transferability to different phases can approach that of quantum
mechanical methods. This potential is similar to the original BOP
@ -53,47 +53,50 @@ discussed below.
The BOP potential consists of three terms:
.. image:: Eqs/pair_bop.jpg
:align: center
.. math::
where phi\_ij(r\_ij) is a short-range two-body function representing the
repulsion between a pair of ion cores, beta\_(sigma,ij)(r\_ij) and
beta\_(sigma,ij)(r\_ij) are respectively sigma and pi bond integrals,
THETA\_(sigma,ij) and THETA\_(pi,ij) are sigma and pi bond-orders, and
U\_prom is the promotion energy for sp-valent systems.
E = \frac{1}{2} \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \phi_{ij} \left( r_{ij} \right) - \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \beta_{\sigma,ij} \left( r_{ij} \right) \cdot \Theta_{\sigma,ij} - \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \beta_{\pi,ij} \left( r_{ij} \right) \cdot \Theta_{\pi,ij} + U_{prom}
where :math:`\phi_{ij}(r_{ij})` is a short-range two-body function
representing the repulsion between a pair of ion cores,
:math:`\beta_{\sigma,ij}(r_{ij})` and :math:`\beta_{\sigma,ij}(r_{ij})`
are respectively sigma and :math:`\pi` bond integrals, :math:`\Theta_{\sigma,ij}`
and :math:`\Theta_{\pi,ij}` are :math:`\sigma` and :math:`\pi`
bond-orders, and U\_prom is the promotion energy for sp-valent systems.
The detailed formulas for this potential are given in Ward
(:ref:`Ward <Ward>`); here we provide only a brief description.
The repulsive energy phi\_ij(r\_ij) and the bond integrals
beta\_(sigma,ij)(r\_ij) and beta\_(phi,ij)(r\_ij) are functions of the
interatomic distance r\_ij between atom i and j. Each of these
potentials has a smooth cutoff at a radius of r\_(cut,ij). These
The repulsive energy :math:`\phi_{ij}(r_{ij})` and the bond integrals
:math:`\beta_{\sigma,ij}(r_{ij})` and :math:`\beta_{\phi,ij}(r_{ij})` are functions of the
interatomic distance :math:`r_{ij}` between atom *i* and *j*\ . Each of these
potentials has a smooth cutoff at a radius of :math:`r_{cut,ij}. These
smooth cutoffs ensure stable behavior at situations with high sampling
near the cutoff such as melts and surfaces.
The bond-orders can be viewed as environment-dependent local variables
that are ij bond specific. The maximum value of the sigma bond-order
(THETA\_sigma) is 1, while that of the pi bond-order (THETA\_pi) is 2,
attributing to a maximum value of the total bond-order
(THETA\_sigma+THETA\_pi) of 3. The sigma and pi bond-orders reflect the
ubiquitous single-, double-, and triple- bond behavior of
chemistry. Their analytical expressions can be derived from tight-
binding theory by recursively expanding an inter-site Green's function
as a continued fraction. To accurately represent the bonding with a
computationally efficient potential formulation suitable for MD
simulations, the derived BOP only takes (and retains) the first two
levels of the recursive representations for both the sigma and the pi
bond-orders. Bond-order terms can be understood in terms of molecular
orbital hopping paths based upon the Cyrot-Lackmann theorem
(:ref:`Pettifor\_1 <Pettifor_1>`). The sigma bond-order with a half-full
valence shell is used to interpolate the bond-order expression that
incorporated explicit valance band filling. This pi bond-order
expression also contains also contains a three-member ring term that
allows implementation of an asymmetric density of states, which helps
to either stabilize or destabilize close-packed structures. The pi
bond-order includes hopping paths of length 4. This enables the
incorporation of dihedral angles effects.
that are ij bond specific. The maximum value of the :math:`\sigma`
bond-order (:math:`\Theta_{\sigma}` is 1, while that of the :math:`\pi`
bond-order (:math:`\Theta_{\pi}`) is 2, attributing to a maximum value
of the total bond-order (:math:`\Theta_{\sigma}+\Theta_{\pi}`) of 3.
The :math:`\sigma` and :math:`\pi` bond-orders reflect the ubiquitous
single-, double-, and triple- bond behavior of chemistry. Their
analytical expressions can be derived from tight- binding theory by
recursively expanding an inter-site Green's function as a continued
fraction. To accurately represent the bonding with a computationally
efficient potential formulation suitable for MD simulations, the derived
BOP only takes (and retains) the first two levels of the recursive
representations for both the :math:`\sigma` and the :math:`\pi` bond-orders. Bond-order
terms can be understood in terms of molecular orbital hopping paths
based upon the Cyrot-Lackmann theorem (:ref:`Pettifor\_1 <Pettifor_1>`).
The :math:`\sigma` bond-order with a half-full valence shell is used to
interpolate the bond-order expression that incorporated explicit valance
band filling. This :math:`\pi` bond-order expression also contains also contains
a three-member ring term that allows implementation of an asymmetric
density of states, which helps to either stabilize or destabilize
close-packed structures. The :math:`\pi` bond-order includes hopping paths of
length 4. This enables the incorporation of dihedral angles effects.
.. note::

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@ -102,11 +102,15 @@ Description
The *born* style computes the Born-Mayer-Huggins or Tosi/Fumi
potential described in :ref:`(Fumi and Tosi) <FumiTosi>`, given by
.. image:: Eqs/pair_born.jpg
:align: center
.. math::
where sigma is an interaction-dependent length parameter, rho is an
ionic-pair dependent length parameter, and Rc is the cutoff.
E = A \exp \left(\frac{\sigma - r}{\rho} \right) -
\frac{C}{r^6} + \frac{D}{r^8} \qquad r < r_c
where :math:`\sigma` is an interaction-dependent length parameter,
:math:`\rho` is an ionic-pair dependent length parameter, and
:math:`r_c` is the cutoff.
The styles with *coul/long* or *coul/msm* add a Coulombic term as
described for the :doc:`lj/cut <pair_lj>` pair styles. An additional
@ -138,8 +142,8 @@ above, or in the data file or restart files read by the
commands, or by mixing as described below:
* A (energy units)
* rho (distance units)
* sigma (distance units)
* :math:`\rho` (distance units)
* :math:`\sigma` (distance units)
* C (energy units \* distance units\^6)
* D (energy units \* distance units\^8)
* cutoff (distance units)

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@ -109,11 +109,13 @@ Description
The *buck* style computes a Buckingham potential (exp/6 instead of
Lennard-Jones 12/6) given by
.. image:: Eqs/pair_buck.jpg
:align: center
.. math::
where rho is an ionic-pair dependent length parameter, and Rc is the
cutoff on both terms.
E = A e^{-r / \rho} - \frac{C}{r^6} \qquad r < r_c
where :math:`\rho` is an ionic-pair dependent length parameter, and
:math:`r_c` is the cutoff on both terms.
The styles with *coul/cut* or *coul/long* or *coul/msm* add a
Coulombic term as described for the :doc:`lj/cut <pair_lj>` pair styles.
@ -147,14 +149,14 @@ above, or in the data file or restart files read by the
commands:
* A (energy units)
* rho (distance units)
* :math:`\rho` (distance units)
* C (energy-distance\^6 units)
* cutoff (distance units)
* cutoff2 (distance units)
The second coefficient, rho, must be greater than zero.
The coefficients A, rho, and C can be written as analytical expressions
of epsilon and sigma, in analogy to the Lennard-Jones potential
The second coefficient, :math:`\rho`, must be greater than zero.
The coefficients A,:math:`\rho`, and C can be written as analytical expressions
of :math:`\epsilon` and :math:`\sigma`, in analogy to the Lennard-Jones potential
:ref:`(Khrapak) <Khrapak>`.
The latter 2 coefficients are optional. If not specified, the global

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@ -50,12 +50,14 @@ interactions following the MOF-FF force field after
:ref:`(Schmid) <Schmid>`. The vdW term of the *buck6d* styles
computes a dispersion damped Buckingham potential:
.. image:: Eqs/pair_buck6d.jpg
:align: center
.. math::
where A and C are a force constant, kappa is an ionic-pair dependent
E = A e^{-\kappa r} - \frac{C}{r^6} \cdot \frac{1}{1 + D r^{14}} \qquad r < r_c \\
where A and C are a force constant, :math:`\kappa` is an ionic-pair dependent
reciprocal length parameter, D is a dispersion correction parameter,
and the cutoff Rc truncates the interaction distance.
and the cutoff :math:`r_c` truncates the interaction distance.
The first term in the potential corresponds to the Buckingham
repulsion term and the second term to the dispersion attraction with
a damping correction analog to the Grimme correction used in DFT.
@ -78,14 +80,16 @@ distributions which effectively dampen electrostatic interactions
for high charges at close distances. The electrostatic potential
is thus evaluated as:
.. image:: Eqs/pair_coul_gauss.jpg
:align: center
.. math::
where C is an energy-conversion constant, Qi and Qj are the
charges on the 2 atoms, epsilon is the dielectric constant which
can be set by the :doc:`dielectric <dielectric>` command, alpha is
ion pair dependent damping parameter and erf() is the error-function.
The cutoff Rc truncates the interaction distance.
E = \frac{C_{q_i q_j}}{\epsilon r_{ij}}\,\, \textrm{erf}\left(\alpha_{ij} r_{ij}\right)\quad\quad\quad r < r_c
where C is an energy-conversion constant, :math:`q_i` and :math:`q_j`
are the charges on the 2 atoms, epsilon is the dielectric constant which
can be set by the :doc:`dielectric <dielectric>` command, alpha is ion
pair dependent damping parameter and erf() is the error-function. The
cutoff Rc truncates the interaction distance.
The style *buck6d/coul/gauss/dsf* computes the Coulomb interaction
via the damped shifted force model described in :ref:`(Fennell) <Fennell>`
@ -107,14 +111,14 @@ above, or in the data file or restart files read by the
commands:
* A (energy units)
* rho (distance\^-1 units)
* :math:`\rho` (distance\^-1 units)
* C (energy-distance\^6 units)
* D (distance\^14 units)
* alpha (distance\^-1 units)
* :math:`\alpha` (distance\^-1 units)
* cutoff (distance units)
The second coefficient, rho, must be greater than zero. The latter
coefficient is optional. If not specified, the global vdW cutoff
The second coefficient, :math:`\rho`, must be greater than zero. The
latter coefficient is optional. If not specified, the global vdW cutoff
is used.

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@ -160,8 +160,21 @@ artifacts.
the CHARMM force field energies and forces, when using one of these
two CHARMM pair styles.
.. image:: Eqs/pair_charmm.jpg
:align: center
.. math::
E = & LJ(r) \qquad \qquad \qquad r < r_{\rm in} \\
= & S(r) * LJ(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
= & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
E = & C(r) \qquad \qquad \qquad r < r_{\rm in} \\
= & S(r) * C(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
= & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
LJ(r) = & 4 \epsilon \left[ \left(\frac{\sigma}{r}\right)^{12} -
\left(\frac{\sigma}{r}\right)^6 \right] \\
C(r) = & \frac{C q_i q_j}{ \epsilon r} \\
S(r) = & \frac{ \left[r_{\rm out}^2 - r^2\right]^2
\left[r_{\rm out}^2 + 2r^2 - 3{r_{\rm in}^2}\right]}
{ \left[r_{\rm out}^2 - {r_{\rm in}}^2\right]^3 }
where S(r) is the energy switching function mentioned above for the
*charmm* styles. See the :ref:`(Steinbach) <Steinbach>` paper for the
@ -209,14 +222,13 @@ above, or in the data file or restart files read by the
:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
commands, or by mixing as described below:
* epsilon (energy units)
* sigma (distance units)
* epsilon\_14 (energy units)
* sigma\_14 (distance units)
* :math:`\epsilon` (energy units)
* :math:`\sigma` (distance units)
* :math:`\epsilon_{14}` (energy units)
* :math:`\sigma_{14}` (distance units)
Note that sigma is defined in the LJ formula as the zero-crossing
distance for the potential, not as the energy minimum at 2\^(1/6)
sigma.
Note that :math:`\sigma` is defined in the LJ formula as the zero-crossing
distance for the potential, not as the energy minimum at :math:`2^{1/6} \sigma`.
The latter 2 coefficients are optional. If they are specified, they
are used in the LJ formula between 2 atoms of these types which are

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@ -82,10 +82,14 @@ Description
The *lj/class2* styles compute a 6/9 Lennard-Jones potential given by
.. image:: Eqs/pair_class2.jpg
:align: center
.. math::
Rc is the cutoff.
E = \epsilon \left[ 2 \left(\frac{\sigma}{r}\right)^9 -
3 \left(\frac{\sigma}{r}\right)^6 \right]
\qquad r < r_c
:math:`r_c` is the cutoff.
The *lj/class2/coul/cut* and *lj/class2/coul/long* styles add a
Coulombic term as described for the :doc:`lj/cut <pair_lj>` pair styles.
@ -98,8 +102,8 @@ above, or in the data file or restart files read by the
:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
commands, or by mixing as described below:
* epsilon (energy units)
* sigma (distance units)
* :math:`\epsilon` (energy units)
* :math:`\sigma` (distance units)
* cutoff1 (distance units)
* cutoff2 (distance units)
@ -121,11 +125,12 @@ specified in the pair\_style command.
If the pair\_coeff command is not used to define coefficients for a
particular I != J type pair, the mixing rule for epsilon and sigma for
all class2 potentials is to use the *sixthpower* formulas documented
by the :doc:`pair_modify <pair_modify>` command. The :doc:`pair_modify mix <pair_modify>` setting is thus ignored for class2 potentials
for epsilon and sigma. However it is still followed for mixing the
cutoff distance.
particular I != J type pair, the mixing rule for :math:`\epsilon` and
:math:`\sigma` for all class2 potentials is to use the *sixthpower*
formulas documented by the :doc:`pair_modify <pair_modify>` command.
The :doc:`pair_modify mix <pair_modify>` setting is thus ignored for
class2 potentials for epsilon and sigma. However it is still followed
for mixing the cutoff distance.
----------