来源：ACS Publications
Developing high-performance mid-infrared nonlinear optical (NLO) crystals is crucial for modern laser technology. Here, three novel salt-inclusion Eu-based chalcogenides (SICs) were successfully synthesized via a guest-framework modulation strategy: [KEu4Cl][Ge3S10] (1), [Eu4Cl2][Ge3S9] (2), and [Eu7Cl2][Ge6Se18] (3). They exhibit diverse structures, where the [Ge2Se6]4– dimer violates Pauling’s third rule. 1–3 exhibit SHG responses of 0.3–0.9 × AGS and suitable bandgaps of 1.88–2.15 eV. Notably, 3 is the first Ge-containing SIC to demonstrate phase-matching behavior. Theoretical calculations reveal that the [Ge2Se6]4– dimer in 3 exhibits enhanced polarizability anisotropy and hyperpolarizability due to its unique connectivity mode. This work systematically demonstrates the potential of rare-earth elements in expanding the structural diversity of SICs and optimizing their NLO properties.