Despite extensive research, the precise spin Hamiltonian of the van der Waals antiferromagnet ${\mathrm{NiPS}}_3$—which hosts a zigzag-ordered ground state—remains debated. While consensus has emerged on ferromagnetic nearest-neighbor ($J_1$) and antiferromagnetic third-nearest-neighbor ($J_3$) Heisenberg interactions, recent studies suggest that a biquadratic ($B$) exchange term may also play a role, though its estimated magnitude varies widely. To address this controversy, we perform density functional theory calculations and extract a positive biquadratic interaction with $B/J_3\approx 0.44$. Within the minimal $J_1\text{−}{J}_3\text{−}B$ model, we show that these parameters naturally stabilize zigzag ordering using minimally augmented spin-wave theory. Density-matrix renormalization group calculations further validate our extracted parameters as a reasonable description of the ground state. Although fully resolving the spin Hamiltonian of ${\mathrm{NiPS}}_3$ requires further investigation, our findings provide insights into its biquadratic interaction.

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• Density matrix renormalization group
• Density of states
• Magnetic interactions
• Magnetic order
• Density functional calculations
• Density functional theory
• Linear spin wave theory
• Monte Carlo methods