Ab Initio Investigation of Pressure Effects in the Spin-Liquid Candidate Y-Kapellasite

Abstract

Motivated by recent experiments showing pressure-induced suppression of magnetic order and the emergence of a dynamical ground state in the anisotropic kagome antiferromagnet Y-kapellasite Y3Cu9(OH)19Cl8, we perform ab initio density functional theory (DFT)calculations to investigate the evolution of magnetic exchange interactions under hydrostatic pressure. We show that pressure efficiently tunes the magnetic Hamiltonian by altering the CuOCu bond geometry, thereby driving the system towards a spin-liquid regime. This evolution is governed by a nonlinear dependence of the dominant exchange coupling on the CuOCu bond angle. We further examine the influence of hydrogen positions and find that both the OH bond length and the hydrogen out-of-plane angle strongly affect the magnetic interactions. Our results provide a microscopic explanation for the experimentally observed pressure-induced enhancement of frustration and highlight the key role of hydrogen geometry.