How to add basis functions with the python interface

Hi libmsym developers,

I am trying to use the python interface to create SALCs. First, I find the point group, so I guess the library is linked correctly. I am having trouble using the python binding to add basis functions to generate the SALCS.

I can see in the example that the basis function is added with the function:

def set_basis(element):  
    basis_function = msym.RealSphericalHarmonic(element = element, name = "1s")  
    element.basis_functions = [basis_function]  
    return basis_function

But this works for one basis set. Lets say I want to create SALCS for Li2 with 1s, 2s and 2p orbitals, the following does not work:

def set_basis_msym(element):
   basis_function = msym.RealSphericalHarmonic(element = element,n=2,l=1,m=1, name = "2px")
   basis_function = msym.RealSphericalHarmonic(element = element,n=2,l=1,m=0, name = "2pz")
   basis_function = msym.RealSphericalHarmonic(element = element,n=2,l=1,m=-1, name = "2py")
   basis_function = msym.RealSphericalHarmonic(element = element,n=2,l=0,m=0, name = "2s")
   basis_function = msym.RealSphericalHarmonic(element = element,n=1,l=0,m=0, name = "1s")
   element.basis_functions = [basis_function]
   return basis_function

I get only a 2x2 matrix for SALCS, that means that I am overwriting the information in the basis_function variable and adding only 1s orbitals.

Also, I could not find the basis_function inside the element class. Sorry if I missed something.

What is the correct way to add more than one basis function for each element?

Thanks in advance.

This is more related to general python code than libmsym but:

The elements contain a list of basis functions (element.basis_functions = [basis_function]) Your code is just repeatedly assigning to a local variable, the last of which is then used. You need to assign to different variables along the lines of:

def set_basis_msym(element):
   px = msym.RealSphericalHarmonic(element = element,name = "2px")
   pz = msym.RealSphericalHarmonic(element = element,name = "2pz")
   py = msym.RealSphericalHarmonic(element = element,name = "2py")
   s2 = msym.RealSphericalHarmonic(element = element,name = "2s")
   s1 = msym.RealSphericalHarmonic(element = element,name = "1s")
   bf_list = [px,pz,py,s2,s1]
   element.basis_functions = bf_list
   return bf_list

Since the above now returns a list you need to flatten the list of basis functions you provide to the context:

basis_functions = [f for e in elements for f in set_basis_msym(e)]
...
with msym.Context(elements = elements, basis_functions = basis_functions) as ctx:

mcodev31 / libmsym

How to add basis functions with the python interface #11