doc for lambda_q and lambda_z

Author: brucefan1983

doc/nep/input_parameters/index.rst

@@ -28,6 +28,8 @@ Below you can find a listing of keywords for the ``nep.in`` input file.
    lambda_e
    lambda_f
    lambda_v
+   lambda_q
+   lambda_z
    atomic_v
    lambda_shear
    force_delta

doc/nep/input_parameters/lambda_q.rst

@@ -0,0 +1,15 @@
+.. _kw_lambda_q:
+.. index::
+   single: lambda_q (keyword in nep.in)
+
+:attr:`lambda_q`
+================
+
+This keyword sets the weight :math:`\lambda_q` of the loss term associated with the **total charge** (the charge for a whole structure) in the :ref:`loss function <nep_loss_function>`.
+The syntax is::
+
+  lambda_q <weight>
+
+Here, :attr:`<weight>` represents :math:`\lambda_q`, which must satisfy :math:`\lambda_q \geq 0` and defaults to :math:`\lambda_f = 0.1`.
+
+This keyword is only relevant for the qNEP models.

doc/nep/input_parameters/lambda_z.rst

@@ -0,0 +1,15 @@
+.. _kw_lambda_z:
+.. index::
+   single: lambda_z (keyword in nep.in)
+
+:attr:`lambda_z`
+================
+
+This keyword sets the weight :math:`\lambda_z` of the loss term associated with the **Born effective charge** in the :ref:`loss function <nep_loss_function>`.
+The syntax is::
+
+  lambda_z <weight>
+
+Here, :attr:`<weight>` represents :math:`\lambda_z`, which must satisfy :math:`\lambda_z \geq 0` and defaults to :math:`\lambda_z = 0.1`.
+
+This keyword is only relevant for the qNEP models.