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--- interactions:angular_pair_potentials [2018/01/06 10:39] – ↷ Page moved from angular_pair_potentials to interactions:angular_pair_potentials daniel
+++ interactions:angular_pair_potentials [2018/01/06 11:04] (current) – daniel
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-The way the angular pair potentials are implemented is similar as how it was done for the MEAM potential.
+The angular pair potentials are a combination of the regular pair potentials and a angular dependent term similar to MEAM:
-The Pair+Angles component is precisely
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-Coulomb interactions are computed the same as in all the others electrostatic models.
+With this approach it is possible to fit potentials such as this one [[http://www.sciencedirect.com/science/article/pii/S0022309396006047|here]].
-With this approach we can consider immediately potentials such as the one used [here](http://www.sciencedirect.com/science/article/pii/S0022309396006047). It will be required only to introduce the special exponentials in eq. (2) in functions.c.
+Or it can be used to consider non-bonded angular interactions as DL_POLY does for the three-body terms (see 'tbp' interaction, p. 174 in the [[http://goo.gl/3ns4i0|manual]]). This can be achieved defining the $f_{ij} = 1$ between the pairs that will form 'triple-bonds' and with their cutoff controlling the central radius to account for angular bonded neighbours. Then, just choosing the $g$ function as an harmonic one.
-Or we can use it to consider non-bonded angular interactions as DL_POLY does for the three-body terms (see 'tbp' interaction, p. 174 in the [manual](http://goo.gl/3ns4i0) ). This can be achieved defining the f_ij = 1 between the pairs that will form 'triple-bonds' and with their cutoff controlling the central radius to account for angular bonded neighbours. Then, just choosing the _g_ function as an harmonic one.
-In addition only for these interactions, I modified the way the threebody neighbours list are created in configs.c, by just adding the neighbours that fall inside the f_ij cutoff radius. This way a lot of memory (and time in _for_ loops) is saved for the systems with several species but angular interactions between only two types of them. And even in the case of having only two species, the angular interactions are usually considered among closest neighbours than the pair interactions, so we benefit of having a smaller angular-neighbours-list in this case also.
-I added a couple of new functions also, an harmonic (despite parabola can contain this, I think is useful to have the classic formula), a Born-Mayer function, and an _acos(r)_ harmonic. The latter, by applying  _acos_ to the argument, is useful for defining an angular _g_ function acting on the angle itself.
 ===== Number of potential functions =====