Programme

P.71 -- Posters, VCTP-51

Date: Thursday, 6 August 2026

Time: 09:30 - 10:30

Energy-Based Downfolding with One-Body MP2 for Molecular and Periodic Systems

Vu Cong Ngoc Thai (1)

(1) Phenikaa Institute for Advanced Study, Phenikaa University, Hanoi 12116, Vietnam

We present an ab initio downfolding framework based on orbital-optimized second-order Møller-Plesset perturbation theory (OBMP2) for constructing low-energy effective Hamiltonians. For molecular systems, dynamical correlation effects outside the active space are incorporated through an OBMP2-derived correlated potential, yielding compact Hamiltonians suitable for accurate many-body solvers. The approach is further generalized to periodic systems through k-point OBMP2 (kOBMP2), where downfolding is performed directly in Bloch space using an energy-based selection of target bands. The resulting effective Hamiltonians are transformed into localized Wannier representations and truncated in real space to generate finite lattice models. This unified framework provides an efficient route for reducing the complexity of correlated molecular and crystalline systems while retaining the essential low-energy physics required for advanced many-body calculations.

Presenter: Vũ Công Ngọc Thái