Solved by ptrblck in post #7 
              
              
                Although the tensor was defined in the __init__ method, it won’t show in the interal parameters: 
class Dan(nn.Module):
    def __init__(self):
        super(Dan, self).__init__()
        self.alpha = torch.tensor(0.5, requires_grad=True)

model = Dan()
print(list(model.parameters()))
> []

As @Mazh…