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### pair_style smd/ulsph command

Syntax:

    pair_style smd/ulsph args

- these keywords must be given

  keyword = *DENSITY_SUMMATION or *DENSITY_CONTINUITY and *VELOCITY_GRADIENT or *NO_VELOCITY_GRADIENT and *GRADIENT_CORRECTION or *NO_GRADIENT_CORRECTION

  Examples:

  pair_style smd/ulsph *DENSITY_CONTINUITY *VELOCITY_GRADIENT *NO_GRADIENT_CORRECTION

  Description:

  The smd/ulsph style computes particle interactions according to continuum mechanics constitutive laws and an updated Lagrangian Smooth-Particle Hydrodynamics algorithm.

  This pair style is invoked similar to the following command:

      pair_style smd/ulsph *DENSITY_CONTINUITY *VELOCITY_GRADIENT *NO_GRADIENT_CORRECTION
      pair_coeff i j *COMMON rho0 c0 Q1 Cp hg &
                     *END

  Here, i and j denote the LAMMPS particle types for which this pair style is defined. Note that i and j can be different, i.e., ulsph cross interactions between different particle types are allowed. However, i--i respectively j--j pair_coeff lines have to preceed a cross interaction. In contrast to the usual LAMMPS pair coeff definitions, which are given solely a number of floats and integers, the ulsph pair coeff definition is organised using keywords. These keywords mark the beginning of different sets of parameters for particle properties, material constitutive models, and damage models. The pair coeff line must be terminated with the *END keyword. The use the line continuation operator & is recommended. A typical invocation of the ulsph for a solid body would consist of an equation of state for computing the pressure (the diagonal components of the stress tensor), and a material model to compute shear stresses (the off-diagonal components of the stress tensor).

  Note that the use of *GRADIENT_CORRECTION can lead to severe numerical instabilities. For a general fluid simulation, *NO_GRADIENT_CORRECTION is recommended.

  Please see the SMD user guide for a complete listing of the possible keywords and material models.

  Mixing, shift, table, tail correction, restart, rRESPA info:

  No mixing is performed automatically. Currently, no part of USER-SMD supports restarting nor minimization. rRESPA does not apply to this pair style.

  Restrictions:

  This fix is part of the USER-SMD package. It is only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info.

  Related commands:

  pair_coeff

  Default: none