# NDmaterialCommand
```tcl
nDMaterial matType? arg1? ...
```
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Currently, only one multi-axial material model has been extended for
DDM-based FE response sensitivity computation.
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MultiYieldSurfaceClay
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The ‘MultiYieldSurfaceClay’ is an elastic-plastic material in which
plasticity exhibits only in the deviatoric stress-strain response. The
volumetric stress-strain response is linear-elastic and is independent
of the deviatoric response. This material is implemented to simulate
monotonic or cyclic response of materials whose shear behavior is
pressure independent. Such materials include, for example, organic soils
or clay under fast (undrained) loading conditions.
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This material is available for sensitivity computation in both 2-D and
3-D models. It is another version of PressureIndependMultiYield
material. However there are three differences between this model and
PressureIndependMultiYield:
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1. This model uses the consistent tangent modulus instead of the
continuum tangent modulus.
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2. This model does not support the ‘updateMaterialStage’ command.
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3. This model does not support further discretization of the strain
increment in each iteration.