Convention

For the theoretical background of the convention problem and why it is important see Convention problem.

Magnopy implements a compact Convention class to store the convention of the spin Hamiltonian. It stores all parameters that define convention in one data structure.

>>> from magnopy import Convention
>>> convention = Convention(multiple_counting = True, spin_normalized = False, c1 = 1, c21 = 1)
>>> convention.name
'custom'
>>> convention.multiple_counting
True
>>> convention.c21
1.0
>>> convention.summary()
custom convention where
  * Bonds are counted multiple times in the sum;
  * Spin vectors are not normalized;
  * c1 = 1.0;
  * c21 = 1.0;
  * Undefined c22 factor;
  * Undefined c31 factor;
  * Undefined c32 factor;
  * Undefined c33 factor;
  * Undefined c41 factor;
  * Undefined c421 factor;
  * Undefined c422 factor;
  * Undefined c43 factor;
  * Undefined c44 factor.

There are two boolean properties (Convention.multiple_counting and Convention.spin_normalized) and eleven constants that fully define the convention of the spin Hamiltonian.

Convention is one of three objects that are required for the creation of the SpinHamiltonian class. It is stored as an its attribute SpinHamiltonian.convention.

Modified convention

Every instance of the convention class is meant to be static, therefore the properties of the convention can not be changed

>>> convention.multiple_counting = False
Traceback (most recent call last):
...
AttributeError: It is intentionally forbidden to set properties of convention. Use correct methods of SpinHamiltonian class to change convention.

If you need to have a new convention, then create a new instance of the Convention class.

For that purpose convention class has a method Convention.get_modified() that allows you to change several properties of convention while keeping the other ones intact

>>> new_convention = convention.get_modified(c1=-1.0, c33 = 1.0)
>>> new_convention.summary()
custom convention where
  * Bonds are counted multiple times in the sum;
  * Spin vectors are not normalized;
  * c1 = -1.0;
  * c21 = 1.0;
  * Undefined c22 factor;
  * Undefined c31 factor;
  * Undefined c32 factor;
  * c33 = 1.0;
  * Undefined c41 factor;
  * Undefined c421 factor;
  * Undefined c422 factor;
  * Undefined c43 factor;
  * Undefined c44 factor.

Pre-defined conventions

Magnopy gives access to the predefined conventions of the spin Hamiltonian from other popular codes

>>> tb2j_convention = Convention.get_predefined("tb2j")
>>> vampire_convention = Convention.get_predefined("vampire")
>>> tb2j_convention.summary()
tb2j convention where
  * Bonds are counted multiple times in the sum;
  * Spin vectors are normalized to 1;
  * Undefined c1 factor;
  * c21 = -1.0;
  * c22 = -1.0;
  * Undefined c31 factor;
  * Undefined c32 factor;
  * Undefined c33 factor;
  * Undefined c41 factor;
  * Undefined c421 factor;
  * Undefined c422 factor;
  * Undefined c43 factor;
  * Undefined c44 factor.
>>> vampire_convention.summary()
vampire convention where
  * Bonds are counted multiple times in the sum;
  * Spin vectors are normalized to 1;
  * Undefined c1 factor;
  * c21 = -1.0;
  * c22 = -0.5;
  * Undefined c31 factor;
  * Undefined c32 factor;
  * Undefined c33 factor;
  * Undefined c41 factor;
  * Undefined c421 factor;
  * Undefined c422 factor;
  * Undefined c43 factor;
  * Undefined c44 factor.

To see all supported codes see Convention.get_predefined().