The excess orbital energy spectrum (EOES) of the JP-10 exo-chair and exo-boat configurations, which are calculated from their corresponding orbital energy differences, is presented in Figure . The EOES provides valuable insight into the electronic structural changes accompanying the isomerism process through their orbital energies. It is a useful tool to understand the differences in electronic behaviour between isomers, and in this case, highlights energy variations in the valence orbitals of JP-10 between the exo-chair and exo-boat configurations. There are several valence orbitals undergo noticeable energy shifts as indicated in Figure . Notably, these changes are confined mostly to the inner valence orbitals rather than the outer valence region, which is consistent with previous studies . For example, the relatively small shift in the HOMO (38a) of 0.1 kcal/mol indicates that the HOMO plays a less critical role in stability for the exo-chair and exo-boat configurations. However, several inner valence orbitals -specifically those in the 11a-28a range -exhibit large changes. These inner valence orbitals, typically associated with bonding interactions in C-C and C-H bonds, seem to be the primary contributors to the configurational differences between the exo-chair and exo-boat isomers. The orbitals that experience the most significant excess energies (indicated by deviations beyond the ±2.0 kcal/mol threshold, marked by red dashed lines in Figure ) include the 22a and 25a orbitals, suggesting that the orbitals are highly sensitive to the conformational changes in the JP-10 isomers. The alterations in these valence orbitals may be attributed to changes in the spatial arrangement of the isomer pair, particularly the rearrangement of the ring system and the orientation of the flag and boat-tip atoms (C5 and C10). The inner valence orbitals are likely responding to changes in steric interactions, bond angles, and bond lengths that differ between the two isomers . It is also important to note that while the inner valence region experiences significant orbital energy changes, the total electronic energies of the isomers do not undergo drastic changes . This subtlety aligns with the modest energetic difference between the two configurations. As previously discussed, the exo-chair configuration is energetically more stable than the exo-boat configuration by about 1.83 kcal/mol, consistent with the results of earlier studies . The EOES analysis further supports this finding by showing that the electronic structure differences are concentrated in a few specific orbitals, particularly in the inner valence range, which is responsible for this modest but decisive energy difference.