Request for Enhancement: Degree of Freedom Control and Atomic Shear Stress Output

[kpoyang]

I am currently conducting research related to dislocations and need to apply pure shear forces at the boundaries while studying the local shear stress within the simulation domain. I would like to request the developers to consider adding the following two features：

1. An enhancement to the fix parameters to include a degree of freedom selection feature, which would enable users to independently control the degrees of freedom for a specific group of atoms in designated directions (such as x, y, or z).
2. An extension of the compute parameters to provide the capability to output atomic shear stress. Currently, only the diagonal parts of the virial matrix, which represent normal stress, are available. The inclusion of shear stress outputs would provide a more comprehensive understanding of material behavior, particularly in the context of dislocations and defects.