{"action":"created","issue":{"url":"https://api.github.com/repos/pandegroup/openmm/issues/1545","repository_url":"https://api.github.com/repos/pandegroup/openmm","labels_url":"https://api.github.com/repos/pandegroup/openmm/issues/1545/labels{/name}","comments_url":"https://api.github.com/repos/pandegroup/openmm/issues/1545/comments","events_url":"https://api.github.com/repos/pandegroup/openmm/issues/1545/events","html_url":"https://github.com/pandegroup/openmm/issues/1545","id":166933670,"number":1545,"title":"Add CustomAnisotropicNonbondedForce ","user":{"login":"mvanvleet","id":14022320,"avatar_url":"https://avatars.githubusercontent.com/u/14022320?v=3","gravatar_id":"","url":"https://api.github.com/users/mvanvleet","html_url":"https://github.com/mvanvleet","followers_url":"https://api.github.com/users/mvanvleet/followers","following_url":"https://api.github.com/users/mvanvleet/following{/other_user}","gists_url":"https://api.github.com/users/mvanvleet/gists{/gist_id}","starred_url":"https://api.github.com/users/mvanvleet/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mvanvleet/subscriptions","organizations_url":"https://api.github.com/users/mvanvleet/orgs","repos_url":"https://api.github.com/users/mvanvleet/repos","events_url":"https://api.github.com/users/mvanvleet/events{/privacy}","received_events_url":"https://api.github.com/users/mvanvleet/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":1,"created_at":"2016-07-21T22:37:14Z","updated_at":"2016-07-22T05:57:57Z","closed_at":null,"body":"I'm looking to implement a pairwise non-bonded force that depends on both the inter-particle distance and on angles that can be defined with respect to a local reference frame for each atom. Github doesn't do well with math equations, so I've attached a pdf that explains the functional form in detail:\r\n\r\n[pairwise_int_potential.pdf](https://github.com/pandegroup/openmm/files/377134/pairwise_int_potential.pdf)\r\n\r\nFor reasons listed in the document, none of the existing CustomForce functions are sufficient for implementing this functional form. I intend to add a CustomAnisotropicNonbondedForce class which would extend CustomNonbondForce to allow for the following:\r\n\r\n-  In addition to the inter-particle distance r, angles theta12, theta21, phi12, and phi21 would be accepted as arguments in the energy expression.\r\n-  Identically to AmoebaMultipoleForce, local axis definitions could be read in for each particle; these local axis definitions would define the angles listed above.\r\n\r\nI'm planning on implementing this enhancement feature myself (starting from CustomNonbondedForce), however am posting this here for two reasons:\r\n\r\n1. This will be my first time developing in OpenMM, so suggestions from more experienced developers are always welcome.\r\n2. I know a few others in the community that are experimenting with (or are interested in using) anisotropic potentials, and am willing to entertain additional features to the class if anyone is working with similar potentials.\r\n"},"comment":{"url":"https://api.github.com/repos/pandegroup/openmm/issues/comments/234461025","html_url":"https://github.com/pandegroup/openmm/issues/1545#issuecomment-234461025","issue_url":"https://api.github.com/repos/pandegroup/openmm/issues/1545","id":234461025,"user":{"login":"rmcgibbo","id":641278,"avatar_url":"https://avatars.githubusercontent.com/u/641278?v=3","gravatar_id":"","url":"https://api.github.com/users/rmcgibbo","html_url":"https://github.com/rmcgibbo","followers_url":"https://api.github.com/users/rmcgibbo/followers","following_url":"https://api.github.com/users/rmcgibbo/following{/other_user}","gists_url":"https://api.github.com/users/rmcgibbo/gists{/gist_id}","starred_url":"https://api.github.com/users/rmcgibbo/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rmcgibbo/subscriptions","organizations_url":"https://api.github.com/users/rmcgibbo/orgs","repos_url":"https://api.github.com/users/rmcgibbo/repos","events_url":"https://api.github.com/users/rmcgibbo/events{/privacy}","received_events_url":"https://api.github.com/users/rmcgibbo/received_events","type":"User","site_admin":false},"created_at":"2016-07-22T05:57:57Z","updated_at":"2016-07-22T05:57:57Z","body":"Out of curiosity, what are your plans for cutoffs / long range behavior? It's not so important for anisotropic exchange, but a `CustomAnisotropicNonbondedForce` wouldn't be limited to exponentially decaying functions in `r_12`."}}
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