Effect of Charge Transfer and Solvation on X‐Ray Absorption Near‐Edge Spectra in Microsolvated Environment

Electron delocalization in microsolvated clusters can substantially modify the character of electronic states accessed after core excitation. In this work, the K‐edge XANES spectra of [Al(H 2 O) n ] 3+ , with n  = 1–6 complexes, are examined using the fc‐CVS‐EOM‐CCSD and CVS‐ADC(2)‐x methods. We evaluate the influence of progressive hydration within first‐ and second‐shell configurations on the core‐excited electronic structure. Systematic variations occur in spectral properties for excitations into valence‐like 3s, 3p, 4s, and 3d states. The charge–transfer analysis of representative 1s → 3p transitions indicates changes in spatial distribution and degree of excited‐electron delocalization. Our results demonstrate the selective dependence of solvation geometry on governing the Al K‐edge spectral features and the comparative application of highly correlated wave function approaches providing a method‐resolved picture of the underlying microsolvation effect.