Dear all,

As shown in manual, 

"The .cst_ome file contains the matrix elements for electronic interband transitions that are required to
generate the dielectric function and other optical properties, based on the results of a CASTEP job. This
is a binary file which contains the array of matrix elements;M(band1,band2,coord,k,spin). The loop is
over the number of bands (band1, band2), x, y, z components (coord), k-points (nk), and spins (ns)."

and 

"Evaluation of matrix elements
The matrix elements of the position operator that are required to describe the electronic transitions in
Eq. CASTEP 55 may normally be written as matrix elements of the momentum operator allowing
straightforward calculation in reciprocal space. However, this depends on the use of local potentials
(Read and Needs, 1991), while in CASTEP nonlocal potentials are more often used. The corrected form of
thematrix elements is:

Eq. CASTEP 56

= 1/(iwm)*

+ 1/(hbar*w)*<[v_nl,r]>

Ultrasoft pseudopotentials produce an additional contribution to optical matrix elements that is also
included in CASTEP results."

I have two questions:

1. Which matrix is saved to CST_OME file? position or momentum operator?

2. For norm conserving pseudopotentials, is the additional contribution added in matrix?

Best regards.