convert pair style bop to class2
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\documentclass[12pt]{article}
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\begin{document}
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$$
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E = \frac{1}{2} \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \phi_{ij} \left( r_{ij} \right) - \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \beta_{\sigma,ij} \left( r_{ij} \right) \cdot \Theta_{\sigma,ij} - \sum_{i=1}^{N} \sum_{j=i_1}^{i_N} \beta_{\pi,ij} \left( r_{ij} \right) \cdot \Theta_{\pi,ij} + U_{prom}
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$$
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\end{document}
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\documentstyle[12pt]{article}
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\begin{document}
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$$
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E = A \exp \left(\frac{\sigma - r}{\rho} \right) -
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\frac{C}{r^6} + \frac{D}{r^8} \qquad r < r_c
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$$
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\end{document}
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\documentclass[12pt]{article}
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\begin{document}
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$$
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E = A e^{-r / \rho} - \frac{C}{r^6} \qquad r < r_c
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$$
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\end{document}
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\documentclass[12pt]{article}
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\begin{document}
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\pagestyle{empty}
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\begin{eqnarray*}
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E = A e^{-\kappa r} - \frac{C}{r^6} \cdot \frac{1}{1 + D r^{14}} \qquad r < r_c \\
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\end{eqnarray*}
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\end{document}
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\documentclass[12pt]{article}
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\begin{document}
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\begin{eqnarray*}
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E & = & LJ(r) \qquad \qquad \qquad r < r_{\rm in} \\
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& = & S(r) * LJ(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
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& = & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
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E & = & C(r) \qquad \qquad \qquad r < r_{\rm in} \\
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& = & S(r) * C(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
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& = & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
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LJ(r) & = & 4 \epsilon \left[ \left(\frac{\sigma}{r}\right)^{12} -
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\left(\frac{\sigma}{r}\right)^6 \right] \\
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C(r) & = & \frac{C q_i q_j}{ \epsilon r} \\
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S(r) & = & \frac{ \left[r_{\rm out}^2 - r^2\right]^2
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\left[r_{\rm out}^2 + 2r^2 - 3{r_{\rm in}^2}\right]}
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{ \left[r_{\rm out}^2 - {r_{\rm in}}^2\right]^3 }
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\end{eqnarray*}
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\end{document}
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\documentstyle[12pt]{article}
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\begin{document}
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$$
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E = \epsilon \left[ 2 \left(\frac{\sigma}{r}\right)^9 -
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3 \left(\frac{\sigma}{r}\right)^6 \right]
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\qquad r < r_c
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$$
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\end{document}
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@ -36,7 +36,7 @@ Description
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"""""""""""
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The *bop* pair style computes Bond-Order Potentials (BOP) based on
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quantum mechanical theory incorporating both sigma and pi bonding.
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quantum mechanical theory incorporating both :math:`\sigma` and :math:`\pi` bonding.
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By analytically deriving the BOP from quantum mechanical theory its
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transferability to different phases can approach that of quantum
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mechanical methods. This potential is similar to the original BOP
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@ -53,47 +53,50 @@ discussed below.
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The BOP potential consists of three terms:
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.. image:: Eqs/pair_bop.jpg
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:align: center
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.. math::
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where phi\_ij(r\_ij) is a short-range two-body function representing the
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repulsion between a pair of ion cores, beta\_(sigma,ij)(r\_ij) and
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beta\_(sigma,ij)(r\_ij) are respectively sigma and pi bond integrals,
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THETA\_(sigma,ij) and THETA\_(pi,ij) are sigma and pi bond-orders, and
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U\_prom is the promotion energy for sp-valent systems.
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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}
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where :math:`\phi_{ij}(r_{ij})` is a short-range two-body function
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representing the repulsion between a pair of ion cores,
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:math:`\beta_{\sigma,ij}(r_{ij})` and :math:`\beta_{\sigma,ij}(r_{ij})`
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are respectively sigma and :math:`\pi` bond integrals, :math:`\Theta_{\sigma,ij}`
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and :math:`\Theta_{\pi,ij}` are :math:`\sigma` and :math:`\pi`
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bond-orders, and U\_prom is the promotion energy for sp-valent systems.
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The detailed formulas for this potential are given in Ward
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(:ref:`Ward <Ward>`); here we provide only a brief description.
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The repulsive energy phi\_ij(r\_ij) and the bond integrals
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beta\_(sigma,ij)(r\_ij) and beta\_(phi,ij)(r\_ij) are functions of the
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interatomic distance r\_ij between atom i and j. Each of these
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potentials has a smooth cutoff at a radius of r\_(cut,ij). These
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The repulsive energy :math:`\phi_{ij}(r_{ij})` and the bond integrals
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:math:`\beta_{\sigma,ij}(r_{ij})` and :math:`\beta_{\phi,ij}(r_{ij})` are functions of the
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interatomic distance :math:`r_{ij}` between atom *i* and *j*\ . Each of these
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potentials has a smooth cutoff at a radius of :math:`r_{cut,ij}. These
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smooth cutoffs ensure stable behavior at situations with high sampling
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near the cutoff such as melts and surfaces.
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The bond-orders can be viewed as environment-dependent local variables
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that are ij bond specific. The maximum value of the sigma bond-order
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(THETA\_sigma) is 1, while that of the pi bond-order (THETA\_pi) is 2,
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attributing to a maximum value of the total bond-order
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(THETA\_sigma+THETA\_pi) of 3. The sigma and pi bond-orders reflect the
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ubiquitous single-, double-, and triple- bond behavior of
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chemistry. Their analytical expressions can be derived from tight-
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binding theory by recursively expanding an inter-site Green's function
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as a continued fraction. To accurately represent the bonding with a
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computationally efficient potential formulation suitable for MD
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simulations, the derived BOP only takes (and retains) the first two
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levels of the recursive representations for both the sigma and the pi
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bond-orders. Bond-order terms can be understood in terms of molecular
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orbital hopping paths based upon the Cyrot-Lackmann theorem
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(:ref:`Pettifor\_1 <Pettifor_1>`). The sigma bond-order with a half-full
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valence shell is used to interpolate the bond-order expression that
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incorporated explicit valance band filling. This pi bond-order
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expression also contains also contains a three-member ring term that
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allows implementation of an asymmetric density of states, which helps
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to either stabilize or destabilize close-packed structures. The pi
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bond-order includes hopping paths of length 4. This enables the
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incorporation of dihedral angles effects.
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that are ij bond specific. The maximum value of the :math:`\sigma`
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bond-order (:math:`\Theta_{\sigma}` is 1, while that of the :math:`\pi`
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bond-order (:math:`\Theta_{\pi}`) is 2, attributing to a maximum value
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of the total bond-order (:math:`\Theta_{\sigma}+\Theta_{\pi}`) of 3.
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The :math:`\sigma` and :math:`\pi` bond-orders reflect the ubiquitous
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single-, double-, and triple- bond behavior of chemistry. Their
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analytical expressions can be derived from tight- binding theory by
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recursively expanding an inter-site Green's function as a continued
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fraction. To accurately represent the bonding with a computationally
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efficient potential formulation suitable for MD simulations, the derived
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BOP only takes (and retains) the first two levels of the recursive
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representations for both the :math:`\sigma` and the :math:`\pi` bond-orders. Bond-order
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terms can be understood in terms of molecular orbital hopping paths
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based upon the Cyrot-Lackmann theorem (:ref:`Pettifor\_1 <Pettifor_1>`).
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The :math:`\sigma` bond-order with a half-full valence shell is used to
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interpolate the bond-order expression that incorporated explicit valance
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band filling. This :math:`\pi` bond-order expression also contains also contains
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a three-member ring term that allows implementation of an asymmetric
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density of states, which helps to either stabilize or destabilize
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close-packed structures. The :math:`\pi` bond-order includes hopping paths of
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length 4. This enables the incorporation of dihedral angles effects.
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.. note::
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@ -102,11 +102,15 @@ Description
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The *born* style computes the Born-Mayer-Huggins or Tosi/Fumi
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potential described in :ref:`(Fumi and Tosi) <FumiTosi>`, given by
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.. image:: Eqs/pair_born.jpg
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:align: center
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.. math::
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where sigma is an interaction-dependent length parameter, rho is an
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ionic-pair dependent length parameter, and Rc is the cutoff.
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E = A \exp \left(\frac{\sigma - r}{\rho} \right) -
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\frac{C}{r^6} + \frac{D}{r^8} \qquad r < r_c
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where :math:`\sigma` is an interaction-dependent length parameter,
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:math:`\rho` is an ionic-pair dependent length parameter, and
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:math:`r_c` is the cutoff.
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The styles with *coul/long* or *coul/msm* add a Coulombic term as
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described for the :doc:`lj/cut <pair_lj>` pair styles. An additional
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@ -138,8 +142,8 @@ above, or in the data file or restart files read by the
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commands, or by mixing as described below:
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* A (energy units)
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* rho (distance units)
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* sigma (distance units)
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* :math:`\rho` (distance units)
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* :math:`\sigma` (distance units)
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* C (energy units \* distance units\^6)
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* D (energy units \* distance units\^8)
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* cutoff (distance units)
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@ -109,11 +109,13 @@ Description
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The *buck* style computes a Buckingham potential (exp/6 instead of
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Lennard-Jones 12/6) given by
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.. image:: Eqs/pair_buck.jpg
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:align: center
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.. math::
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where rho is an ionic-pair dependent length parameter, and Rc is the
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cutoff on both terms.
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E = A e^{-r / \rho} - \frac{C}{r^6} \qquad r < r_c
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where :math:`\rho` is an ionic-pair dependent length parameter, and
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:math:`r_c` is the cutoff on both terms.
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The styles with *coul/cut* or *coul/long* or *coul/msm* add a
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Coulombic term as described for the :doc:`lj/cut <pair_lj>` pair styles.
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@ -147,14 +149,14 @@ above, or in the data file or restart files read by the
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commands:
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* A (energy units)
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* rho (distance units)
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* :math:`\rho` (distance units)
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* C (energy-distance\^6 units)
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* cutoff (distance units)
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* cutoff2 (distance units)
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The second coefficient, rho, must be greater than zero.
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The coefficients A, rho, and C can be written as analytical expressions
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of epsilon and sigma, in analogy to the Lennard-Jones potential
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The second coefficient, :math:`\rho`, must be greater than zero.
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The coefficients A,:math:`\rho`, and C can be written as analytical expressions
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of :math:`\epsilon` and :math:`\sigma`, in analogy to the Lennard-Jones potential
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:ref:`(Khrapak) <Khrapak>`.
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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
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:ref:`(Schmid) <Schmid>`. The vdW term of the *buck6d* styles
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computes a dispersion damped Buckingham potential:
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.. image:: Eqs/pair_buck6d.jpg
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:align: center
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.. math::
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where A and C are a force constant, kappa is an ionic-pair dependent
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E = A e^{-\kappa r} - \frac{C}{r^6} \cdot \frac{1}{1 + D r^{14}} \qquad r < r_c \\
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where A and C are a force constant, :math:`\kappa` is an ionic-pair dependent
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reciprocal length parameter, D is a dispersion correction parameter,
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and the cutoff Rc truncates the interaction distance.
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and the cutoff :math:`r_c` truncates the interaction distance.
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The first term in the potential corresponds to the Buckingham
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repulsion term and the second term to the dispersion attraction with
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a damping correction analog to the Grimme correction used in DFT.
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@ -78,14 +80,16 @@ distributions which effectively dampen electrostatic interactions
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for high charges at close distances. The electrostatic potential
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is thus evaluated as:
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.. image:: Eqs/pair_coul_gauss.jpg
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:align: center
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.. math::
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where C is an energy-conversion constant, Qi and Qj are the
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charges on the 2 atoms, epsilon is the dielectric constant which
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can be set by the :doc:`dielectric <dielectric>` command, alpha is
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ion pair dependent damping parameter and erf() is the error-function.
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The cutoff Rc truncates the interaction distance.
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E = \frac{C_{q_i q_j}}{\epsilon r_{ij}}\,\, \textrm{erf}\left(\alpha_{ij} r_{ij}\right)\quad\quad\quad r < r_c
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where C is an energy-conversion constant, :math:`q_i` and :math:`q_j`
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are the charges on the 2 atoms, epsilon is the dielectric constant which
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can be set by the :doc:`dielectric <dielectric>` command, alpha is ion
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pair dependent damping parameter and erf() is the error-function. The
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cutoff Rc truncates the interaction distance.
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The style *buck6d/coul/gauss/dsf* computes the Coulomb interaction
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via the damped shifted force model described in :ref:`(Fennell) <Fennell>`
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@ -107,14 +111,14 @@ above, or in the data file or restart files read by the
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commands:
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* A (energy units)
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* rho (distance\^-1 units)
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* :math:`\rho` (distance\^-1 units)
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* C (energy-distance\^6 units)
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* D (distance\^14 units)
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* alpha (distance\^-1 units)
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* :math:`\alpha` (distance\^-1 units)
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* cutoff (distance units)
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The second coefficient, rho, must be greater than zero. The latter
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coefficient is optional. If not specified, the global vdW cutoff
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The second coefficient, :math:`\rho`, must be greater than zero. The
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latter coefficient is optional. If not specified, the global vdW cutoff
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is used.
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@ -160,8 +160,21 @@ artifacts.
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the CHARMM force field energies and forces, when using one of these
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two CHARMM pair styles.
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.. image:: Eqs/pair_charmm.jpg
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:align: center
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.. math::
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E = & LJ(r) \qquad \qquad \qquad r < r_{\rm in} \\
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= & S(r) * LJ(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
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= & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
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E = & C(r) \qquad \qquad \qquad r < r_{\rm in} \\
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= & S(r) * C(r) \qquad \qquad r_{\rm in} < r < r_{\rm out} \\
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= & 0 \qquad \qquad \qquad \qquad r > r_{\rm out} \\
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LJ(r) = & 4 \epsilon \left[ \left(\frac{\sigma}{r}\right)^{12} -
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\left(\frac{\sigma}{r}\right)^6 \right] \\
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C(r) = & \frac{C q_i q_j}{ \epsilon r} \\
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S(r) = & \frac{ \left[r_{\rm out}^2 - r^2\right]^2
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\left[r_{\rm out}^2 + 2r^2 - 3{r_{\rm in}^2}\right]}
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{ \left[r_{\rm out}^2 - {r_{\rm in}}^2\right]^3 }
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where S(r) is the energy switching function mentioned above for the
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*charmm* styles. See the :ref:`(Steinbach) <Steinbach>` paper for the
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@ -209,14 +222,13 @@ above, or in the data file or restart files read by the
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
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commands, or by mixing as described below:
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* epsilon (energy units)
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* sigma (distance units)
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* epsilon\_14 (energy units)
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* sigma\_14 (distance units)
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* :math:`\epsilon` (energy units)
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* :math:`\sigma` (distance units)
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* :math:`\epsilon_{14}` (energy units)
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* :math:`\sigma_{14}` (distance units)
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Note that sigma is defined in the LJ formula as the zero-crossing
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distance for the potential, not as the energy minimum at 2\^(1/6)
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sigma.
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Note that :math:`\sigma` is defined in the LJ formula as the zero-crossing
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distance for the potential, not as the energy minimum at :math:`2^{1/6} \sigma`.
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The latter 2 coefficients are optional. If they are specified, they
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are used in the LJ formula between 2 atoms of these types which are
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@ -82,10 +82,14 @@ Description
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The *lj/class2* styles compute a 6/9 Lennard-Jones potential given by
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.. image:: Eqs/pair_class2.jpg
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:align: center
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.. math::
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Rc is the cutoff.
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E = \epsilon \left[ 2 \left(\frac{\sigma}{r}\right)^9 -
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3 \left(\frac{\sigma}{r}\right)^6 \right]
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\qquad r < r_c
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:math:`r_c` is the cutoff.
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The *lj/class2/coul/cut* and *lj/class2/coul/long* styles add a
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Coulombic term as described for the :doc:`lj/cut <pair_lj>` pair styles.
|
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@ -98,8 +102,8 @@ above, or in the data file or restart files read by the
|
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
|
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commands, or by mixing as described below:
|
||||
|
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* epsilon (energy units)
|
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* sigma (distance units)
|
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* :math:`\epsilon` (energy units)
|
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* :math:`\sigma` (distance units)
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* cutoff1 (distance units)
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* cutoff2 (distance units)
|
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@ -121,11 +125,12 @@ specified in the pair\_style command.
|
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If the pair\_coeff command is not used to define coefficients for a
|
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particular I != J type pair, the mixing rule for epsilon and sigma for
|
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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.
|
||||
|
||||
|
||||
----------
|
||||
|
||||
Reference in New Issue
Block a user