.. index:: compute property/atom compute property/atom command ============================= Syntax """""" .. parsed-literal:: compute ID group-ID property/atom input1 input2 ... * ID, group-ID are documented in :doc:`compute ` command * property/atom = style name of this compute command * input = one or more atom attributes .. parsed-literal:: possible attributes = id, mol, proc, type, mass, x, y, z, xs, ys, zs, xu, yu, zu, ix, iy, iz, vx, vy, vz, fx, fy, fz, q, mux, muy, muz, mu, radius, diameter, omegax, omegay, omegaz, angmomx, angmomy, angmomz, shapex,shapey, shapez, quatw, quati, quatj, quatk, tqx, tqy, tqz, end1x, end1y, end1z, end2x, end2y, end2z, corner1x, corner1y, corner1z, corner2x, corner2y, corner2z, corner3x, corner3y, corner3z, nbonds, vfrac, s0, spin, eradius, ervel, erforce, rho, drho, e, de, cv, i_name, d_name .. parsed-literal:: id = atom ID mol = molecule ID proc = ID of processor that owns atom type = atom type mass = atom mass x,y,z = unscaled atom coordinates xs,ys,zs = scaled atom coordinates xu,yu,zu = unwrapped atom coordinates ix,iy,iz = box image that the atom is in vx,vy,vz = atom velocities fx,fy,fz = forces on atoms q = atom charge mux,muy,muz = orientation of dipole moment of atom mu = magnitude of dipole moment of atom radius,diameter = radius,diameter of spherical particle omegax,omegay,omegaz = angular velocity of spherical particle angmomx,angmomy,angmomz = angular momentum of aspherical particle shapex,shapey,shapez = 3 diameters of aspherical particle quatw,quati,quatj,quatk = quaternion components for aspherical or body particles tqx,tqy,tqz = torque on finite-size particles end12x, end12y, end12z = end points of line segment corner123x, corner123y, corner123z = corner points of triangle nbonds = number of bonds assigned to an atom .. parsed-literal:: PERI package per-atom properties: vfrac = ??? s0 = ??? .. parsed-literal:: USER-EFF and USER-AWPMD package per-atom properties: spin = electron spin eradius = electron radius ervel = electron radial velocity erforce = electron radial force .. parsed-literal:: USER-SPH package per-atom properties: rho = ??? drho = ??? e = ??? de = ??? cv = ??? .. parsed-literal:: :doc:`fix property/atom ` per-atom properties: i_name = custom integer vector with name d_name = custom integer vector with name Examples """""""" .. parsed-literal:: compute 1 all property/atom xs vx fx mux compute 2 all property/atom type compute 1 all property/atom ix iy iz Description """"""""""" Define a computation that simply stores atom attributes for each atom in the group. This is useful so that the values can be used by other :ref:`output commands ` that take computes as inputs. See for example, the :doc:`compute reduce `, :doc:`fix ave/atom `, :doc:`fix ave/histo `, :doc:`fix ave/spatial `, and :doc:`atom-style variable ` commands. The list of possible attributes is the same as that used by the :doc:`dump custom ` command, which describes their meaning, with some additional quantities that are only defined for certain :doc:`atom styles `. Basically, this augmented list gives an input script access to any per-atom quantity stored by LAMMPS. The values are stored in a per-atom vector or array as discussed below. Zeroes are stored for atoms not in the specified group or for quantities that are not defined for a particular particle in the group (e.g. *shapex* if the particle is not an ellipsoid). The additional quantities only accessible via this command, and not directly via the :doc:`dump custom ` command, are as follows. *Shapex*\ , *shapey*\ , and *shapez* are defined for ellipsoidal particles and define the 3d shape of each particle. *Quatw*\ , *quati*\ , *quatj*\ , and *quatk* are defined for ellipsoidal particles and body particles and store the 4-vector quaternion representing the orientation of each particle. See the :doc:`set ` command for an explanation of the quaternion vector. *End1x*\ , *end1y*\ , *end1z*\ , *end2x*\ , *end2y*\ , *end2z*\ , are defined for line segment particles and define the end points of each line segment. *Corner1x*\ , *corner1y*\ , *corner1z*\ , *corner2x*\ , *corner2y*\ , *corner2z*\ , *corner3x*\ , *corner3y*\ , *corner3z*\ , are defined for triangular particles and define the corner points of each triangle. *Nbonds* is available for all molecular atom styles and refers to the number of explicit bonds assigned to an atom. Note that if the :doc:`newton bond ` command is set to *on*\ , which is the default, then every bond in the system is assigned to only one of the two atoms in the bond. Thus a bond between atoms I,J may be tallied for either atom I or atom J. If :doc:`newton bond off ` is set, it will be tallied with both atom I and atom J. The *i_name* and *d_name* attributes refer to custom integer and floating-point properties that have been added to each atom via the :doc:`fix property/atom ` command. When that command is used specific names are given to each attribute which are what is specified as the "name" portion of *i_name* or *d_name*\ . **Output info:** This compute calculates a per-atom vector or per-atom array depending on the number of input values. If a single input is specified, a per-atom vector is produced. If two or more inputs are specified, a per-atom array is produced where the number of columns = the number of inputs. The vector or array can be accessed by any command that uses per-atom values from a compute as input. See :ref:`this section ` for an overview of LAMMPS output options. The vector or array values will be in whatever :doc:`units ` the corresponding attribute is in, e.g. velocity units for vx, charge units for q, etc. Restrictions """""""""""" none Related commands """""""""""""""" :doc:`dump custom `, :doc:`compute reduce `, :doc:`fix ave/atom `, :doc:`fix ave/spatial `, :doc:`fix property/atom ` **Default:** none .. _lws: http://lammps.sandia.gov .. _ld: Manual.html .. _lc: Section_commands.html#comm