Hey there Ahmad Umair! Working on HKL calculations without access to JCPDS cards can be a bit tricky, but it's definitely doable. For orthorhombic and rhombohedral crystals like in your case, one reliable method involves utilizing software packages specifically designed for crystallography analysis.

For orthorhombic crystals, you Ahmad Umair can employ algorithms based on Bravais lattice symmetry to determine the possible Miller indices (HKL) for diffraction peaks. Tools like FullProf or PowderCell can be quite handy for this purpose.

As for rhombohedral crystals, since they have a hexagonal lattice, the calculations become a bit more complex. However, software like Materials Studio or Mercury can assist in generating HKL values based on the crystal structure information.

Additionally, you Ahmad Umair might find some useful algorithms and codes in research papers or online forums where fellow researchers share their methods for HKL calculations in the absence of JCPDS cards.

Remember, precision and accuracy are key in crystallography, so double-checking your results with alternative methods or experimental data is always a good practice. Let me know if you Ahmad Umair need further assistance or clarification on any aspect of your calculations!