1.. index:: improper_coeff 2 3improper_coeff command 4====================== 5 6Syntax 7"""""" 8 9.. code-block:: LAMMPS 10 11 improper_coeff N args 12 13* N = improper type (see asterisk form below) 14* args = coefficients for one or more improper types 15 16Examples 17"""""""" 18 19.. code-block:: LAMMPS 20 21 improper_coeff 1 300.0 0.0 22 improper_coeff * 80.2 -1 2 23 improper_coeff *4 80.2 -1 2 24 25Description 26""""""""""" 27 28Specify the improper force field coefficients for one or more improper 29types. The number and meaning of the coefficients depends on the 30improper style. Improper coefficients can also be set in the data 31file read by the :doc:`read_data <read_data>` command or in a restart 32file. 33 34N can be specified in one of two ways. An explicit numeric value can 35be used, as in the first example above. Or a wild-card asterisk can be 36used to set the coefficients for multiple improper types. This takes 37the form "\*" or "\*n" or "n\*" or "m\*n". If N = the number of improper 38types, then an asterisk with no numeric values means all types from 1 39to N. A leading asterisk means all types from 1 to n (inclusive). A 40trailing asterisk means all types from n to N (inclusive). A middle 41asterisk means all types from m to n (inclusive). 42 43Note that using an improper_coeff command can override a previous 44setting for the same improper type. For example, these commands set 45the coeffs for all improper types, then overwrite the coeffs for just 46improper type 2: 47 48.. code-block:: LAMMPS 49 50 improper_coeff * 300.0 0.0 51 improper_coeff 2 50.0 0.0 52 53A line in a data file that specifies improper coefficients uses the 54exact same format as the arguments of the improper_coeff command in an 55input script, except that wild-card asterisks should not be used since 56coefficients for all N types must be listed in the file. For example, 57under the "Improper Coeffs" section of a data file, the line that 58corresponds to the first example above would be listed as 59 60.. parsed-literal:: 61 62 1 300.0 0.0 63 64The :doc:`improper_style class2 <improper_class2>` is an exception to 65this rule, in that an additional argument is used in the input script 66to allow specification of the cross-term coefficients. See its doc 67page for details. 68 69---------- 70 71The list of all improper styles defined in LAMMPS is given on the 72:doc:`improper_style <improper_style>` doc page. They are also listed 73in more compact form on the :ref:`Commands improper <improper>` doc page. 74 75On either of those pages, click on the style to display the formula it 76computes and its coefficients as specified by the associated 77improper_coeff command. 78 79---------- 80 81Restrictions 82"""""""""""" 83 84This command must come after the simulation box is defined by a 85:doc:`read_data <read_data>`, :doc:`read_restart <read_restart>`, or 86:doc:`create_box <create_box>` command. 87 88An improper style must be defined before any improper coefficients are 89set, either in the input script or in a data file. 90 91Related commands 92"""""""""""""""" 93 94:doc:`improper_style <improper_style>` 95 96Default 97""""""" 98 99none 100