diff --git a/doc/src/pair_coul_tt.rst b/doc/src/pair_coul_tt.rst index 47375d99a4..885cce073e 100644 --- a/doc/src/pair_coul_tt.rst +++ b/doc/src/pair_coul_tt.rst @@ -40,35 +40,34 @@ The *coul/tt* pair style should be used as a sub-style within in the :doc:`pair_style hybrid/overlay ` command, in conjunction with a main pair style including Coulomb interactions and *thole* pair style, or with *lj/cut/thole/long* pair style that is equivalent to the combination -of two preceding. +of preceding two. The *coul/tt* pair styles compute the charge-dipole Coulomb interaction damped at short distances by a function .. math:: - TT_{ij}(r) = 1 - c_{ij} \cdot e^{-b_{ij} r} \sum_{k=0}^n \frac{(b_{ij} r)^k}{k!} + f_{n,ij}(r) = 1 - c_{ij} \cdot e^{-b_{ij} r} \sum_{k=0}^n \frac{(b_{ij} r)^k}{k!} -This function results from an adaptation to Coulomb interaction :ref:`(Salanne) -` the damping function originally proposed -by :ref:`(Tang Toennies) ` for van der Waals interactions. +This function results from an adaptation to the Coulomb interaction :ref:`(Salanne) +` of the damping function originally proposed +by :ref:`Tang Toennies ` for van der Waals interactions. -The polynomial takes the degree of 4 for damping Coulomb interaction. +The polynomial takes the degree 4 for damping the Coulomb interaction. The parameters :math:`b_{ij}` and :math:`c_{ij}` could be determined from first-principle calculations for small, mainly mono-atomic, ions :ref:`(Salanne) -` or chosen as empirical for large molecules. +`, or else treated as empirical for large molecules. -The damping function is typically applied to the interactions between a Drude -charge (:math:`q_{D,i}` on a Drude particle or :math:`-q_{D,i}` on the respective -Drude core particle bonded to a Drude particle) and a charge of a non-polarizable -atom, :math:`q_{j}`. The Tang-Toennies function could be used to damp electrostatic -interaction between two Drude cores acting on the partial charge of the one core -:math:`q_{i}-q_{D,i}` and a Drude charge of the another one :math:`-q_{D,j}`, and -the opposite case, respectively. The :math:`b_{ij}` and :math:`c_{ij}` are equal -to :math:`b_{ji}` and :math:`c_{ji}` in case of core - core interaction. -Therefore, the screening is not applied to the full charge of the Drude core -:math:`q_i`, but only to the :math:`-q_{D,i}` part of it when it acts as a -dipole or :math:`q_{i}-q_{D,i}` when it acts as a charge. +In pair styles with Drude induced dipoles, this damping function is typically +applied to the interactions between a Drude charge (either :math:`q_{D,i}` on +a Drude particle or :math:`-q_{D,i}` on the respective +Drude core)) and a charge on a non-polarizable atom, :math:`q_{j}`. + +The Tang-Toennies function could also be used to damp electrostatic +interactions between the (non-polarizable part of the) charge of a core, +:math:`q_{i}-q_{D,i}`, and the Drude charge of another, :math:`-q_{D,j}`. +The :math:`b_{ij}` and :math:`c_{ij}` are equal to :math:`b_{ji}` and +:math:`c_{ji}` in the case of core-core interactions. For pair_style *coul/tt*\ , the following coefficients must be defined for each pair of atoms types via the :doc:`pair_coeff ` command @@ -80,9 +79,9 @@ as in the example above. * cutoff (distance units) The last two coefficients are optional. If not specified the global -degree of polynomial or global cutoff specified in the pair_style -command are used. In order to specify a cutoff (forth argument) a damp -parameter (third argument) must also be specified. +degree of the polynomial or the global cutoff specified in the pair_style +command are used. In order to specify a cutoff (forth argument), the degree of +the polynomial (third argument) must also be specified. ---------- diff --git a/src/USER-DRUDE/README b/src/USER-DRUDE/README index 53685221b1..179c1e1179 100644 --- a/src/USER-DRUDE/README +++ b/src/USER-DRUDE/README @@ -7,7 +7,7 @@ features: using Langevin or Nosé-Hoover thermostats * computation of the atom and dipole temperatures * damping induced dipole interactions using Thole's function -* charge-dipole damping using Tang-Toennies damping function +* charge-dipole damping using Tang-Toennies function See the file doc/drude_tutorial.html for getting started.