Background: 178Hfm2 isomer is considered the most suitable candidate to study the depletion of its stored energy induced by low-energy X-ray in recent decades. Purpose: The aim is to research whether there exist potential gateway states which may trigger gamma-ray emission from the K?=16+ isomer with low-energy photons. Methods: The projected shell model is at first used to study the multi-quasiparticle and collective excitation states of 178Hf. Results: The results show that the 16+ isomer lies well separated in energy from other states. But when the configuration-constrained (diabatic blocking) calculations

with inclusion of ?-deformation

are performed to study the multi-quasiparticle excitation states of 178Hf

it appears that three levels can be the most likely candidates for photodeexcitation of the 16+ isomer. Conclusion: The Potential Energy Surface (PES) calculations in the present work suggest that this nucleus is rigid to axially asymmetric shapes. Abstract