Brittle fracture can be studied by means of phase-field models, among which we recall low-order functionals which comprise AT1 or AT2 regularizations [1] and high-order AT2 models proposed in [2]. The latter exhibit comparable accuracy to low-order AT2 employing a mesh-size two times larger, thereby reducing the computational effort, while the AT1 model features an elastic limit before the onset of crack growth. Therefore, we present a novel fourth-order AT1 model in an Isogeometric framework, which provides a straightforward discretization of the high-order term in the crack surface density functional. For the proposed AT1 model, we calculate the ad-hoc cw coefficient, which provides Γ-convergence by minimizing the 1D crack surface density. To this end, we solve the associated ODE, compute the interval [0,R] in which the damage profile d∈[0 1] and evaluate the integral of the crack surface energy over [0,R]. All numerical results show that our AT1 model has still comparable accuracy and lower computational cost with respect to the investigated AT2 models. Fracture irreversibility is addressed using PSOR algorithm in all tests [3]. REFERENCES [1] L. Ambrosio, V.M. Tortorelli. Approximation of functional depending on jumps by elliptic functional via Γ-convergence. Communications on Pure and Applied Mathematics 43(8), 999-1036 (1990). [2] M.J. Borden, T.J.R. Hughes, C. Landis, C. Verhoosel. A higher-order phase-field model for brittle fracture: Formulation and analysis within the isogeometric analysis framework. Computer Methods in Applied Mechanics and Engineering, 273: 100-118, 2014. [3] A. Marengo, A. Patton, M. Negri, U. Perego, A. Reali. A rigorous and efficient explicit algorithm for irreversibility enforcement in phase-field finite element modeling of brittle crack propagation. Computer Methods in Applied Mechanics and Engineering, 387: 114137, 2021.