# Sebastian WoutersGhent University | UGhent · Center for Molecular Modeling

Sebastian Wouters

Master of science in engineering physics

## About

29

Publications

9,719

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2,628

Citations

Citations since 2017

Introduction

Additional affiliations

October 2010 - September 2014

Education

October 2005 - June 2010

## Publications

Publications (29)

PySCF is a Python-based general-purpose electronic structure platform that supports first-principles simulations of molecules and solids as well as accelerates the development of new methodology and complex computational workflows. This paper explains the design and philosophy behind PySCF that enables it to meet these twin objectives. With several...

PYSCF is a Python-based general-purpose electronic structure platform that both supports first-principles simulations of molecules and solids, as well as accelerates the development of new methodology and complex computational workflows. The present paper explains the design and philosophy behind PYSCF that enables it to meet these twin objectives....

We present a new variational tree tensor network state (TTNS) ansatz, the three-legged tree tensor network state (T3NS). Physical tensors are interspersed with branching tensors. Physical tensors have one physical index and at most two virtual indices, as in the matrix product state (MPS) ansatz of the density matrix renormalization group (DMRG). B...

Density matrix embedding theory (DMET) is a relatively new technique for the calculation of strongly correlated systems. Recently, block product DMET (BPDMET) was introduced for the study of spin systems such as the antiferromagnetic J1−J2 model on the square lattice. In this paper, we extend the variational Ansatz of BPDMET using spin-state optimi...

Density matrix embedding theory (DMET) is a relatively new technique for the calculation of strongly correlated systems. Recently cluster DMET (CDMET) was introduced for the study of spin systems such as the anti-ferromagnetic $J_1-J_2$ model on the square lattice. In this paper, we study the Kitaev-Heisenberg model on the honeycomb lattice using t...

PySCF is a general-purpose electronic structure platform designed from the ground up to emphasize code simplicity, both to aid new method development, as well as for flexibility in computational workflow. The package provides a wide range of tools to support simulations of finite size systems, extended systems with periodic boundary conditions, low...

Density matrix embedding theory (DMET) describes finite fragments in the presence of a surrounding environment. In contrast to most embedding methods, DMET explicitly allows for quantum entanglement between both. In this chapter, we discuss both the ground-state and response theory formulations of DMET, and review several applications. In addition,...

The complete active space second-order perturbation theory (CASPT2) can be extended to larger active spaces by using the density matrix renormalization group (DMRG) as solver. Two variants are commonly used: the costly DMRG-CASPT2 with exact 4-particle reduced density matrix (4-RDM) and the cheaper DMRG-cu(4)-CASPT2 in which the 4-cumulant is disca...

We have implemented internally contracted complete active space second order perturbation theory (CASPT2) with the density matrix renormalization group (DMRG) as active space solver [Y. Kurashige and T. Yanai, J. Chem. Phys. 135, 094104 (2011)]. Internally contracted CASPT2 requires to contract the generalized Fock matrix with the 4-particle reduce...

Density matrix embedding theory (DMET) describes finite fragments in the presence of a surrounding environment. In contrast to most embedding methods, DMET explicitly allows for quantum entanglement between both. In this chapter, we discuss both the ground-state and response theory formulations of DMET, and review several applications. In addition,...

Density matrix embedding theory (DMET) provides a theoretical framework to treat finite fragments in the presence of a surrounding molecular or bulk environment, even when there is significant correlation or entanglement between the two. In this work, we give a practically oriented and explicit description of the numerical and theoretical formulati...

Despite various studies on the polymerization of poly(p-phenylene vinylene) (PPV) through different precursor routes, detailed mechanistic knowledge on the individual reaction steps and intermediates is still incomplete. The present study aims to gain more insight into the radical polymerization of PPV through the Gilch route. The initial steps of...

The best-known application of salen complexes is the use of a chiral ligand loaded with manganese to form the Jacobsen complex. This organometallic catalyst is used in the epoxidation of unfunctionalized olefins and can achieve very high selectivities. Although this application was proposed many years ago, the mechanism of oxygen transfer remains a...

Jacobsen's complexes are famous for their usability for enantioselective epoxidations. However, the applicability of this catalytic system has been severely limited by several practical problems such as deactivation and separation after reaction. Grafting of Jacobsen-type complexes on solid supports is an attractive way to overcome these problems b...

CheMPS2, our spin-adapted implementation of the density matrix renormalization group (DMRG) for ab initio quantum chemistry (Wouters et al., 2014), has several new features. A speed-up of the augmented Hessian Newton–Raphson DMRG self-consistent field (DMRG-SCF) routine is achieved with the direct inversion of the iterative subspace (DIIS). For ext...

The thermal equilibration of the methyl esters of endiandric acids D and E was subject to a computational study. An electrocyclic pathway via an electrocyclic ring opening followed by a ring flip and a subsequent electrocyclization proposed by Nicolaou [Chem. Soc. Rev. 2009], was computationally explored. The free energy barrier for this electrocyc...

During the past 15 years, the density matrix renormalization group (DMRG) has
become increasingly important for ab initio quantum chemistry. Its underlying
wavefunction ansatz, the matrix product state (MPS), is a low-rank
decomposition of the full configuration interaction tensor. The virtual
dimension of the MPS, the rank of the decomposition, co...

We use CheMPS2, our free open-source spin-adapted implementation of the
density matrix renormalization group (DMRG) [Wouters et al., Comput. Phys.
Commun. 185, 1501 (2014)], to study the lowest singlet, triplet, and quintet
states of the oxo-Mn(Salen) complex. We describe how an initial approximate
DMRG calculation in a large active space around th...

During the past 15 years, the density matrix renormalization group (DMRG) has
become increasingly important for ab initio quantum chemistry. The underlying
matrix product state (MPS) ansatz is a low-rank decomposition of the full
configuration interaction tensor. The virtual dimension of the MPS controls the
size of the corner of the many-body Hilb...

We introduce a marriage of tensor network states (TNS) and projector quantum
Monte Carlo (PMC) to overcome both the high computational scaling of TNS and
the sign problem of PMC. As a specific example, we describe phaseless auxiliary
field quantum Monte Carlo with matrix product states (MPS-AFQMC). MPS-AFQMC
improves significantly on the variationa...

Linear response theory for the density matrix renormalization group (DMRG-LRT) was first presented in terms of the DMRG renormalization projectors [J. J. Dorando, J. Hachmann, and G. K.-L. Chan, J. Chem. Phys. 130, 184111 (2009)]. Later, with an understanding of the manifold structure of the matrix product state (MPS) ansatz, which lies at the basi...

The density matrix renormalization group (DMRG) has become an indispensable
numerical tool to find exact eigenstates of finite-size quantum systems with
strong correlation. In the fields of condensed matter, nuclear structure and
molecular electronic structure, it has significantly extended the system sizes
that can be handled compared to full conf...

The similarities between Hartree-Fock (HF) theory and the density matrix renormalization group (DMRG) are explored. Both methods can be formulated as the variational optimization of a wave-function Ansatz. Linearization of the time-dependent variational principle near a variational minimum allows to derive the random phase approximation (RPA). We s...

The reduced density matrix is variationally optimized for the two-dimensional
Hubbard model. Exploiting all symmetries present in the system, we have been
able to study $6\times6$ lattices at various fillings and different values for
the on-site repulsion, using the highly accurate but computationally expensive
three-index conditions. To reduce the...

The similarities between Hartree-Fock (HF) theory and the density-matrix
renormalization group (DMRG) are explored. Both methods can be formulated as
the variational optimization of a wave-function ansatz. Linearization of the
time-dependent variational principle near a variational minimum allows to
derive the random phase approximation (RPA). We s...

Using variational density matrix optimization with two- and three-index conditions we study the one-dimensional Hubbard model with periodic boundary conditions at various filling factors. Special attention is directed to the full exploitation of the available symmetries, more specifically the combination of translational invariance and space-invers...

We have implemented the sweep algorithm for the variational optimization of SU(2) x U(1) (spin and particle number) invariant matrix product states (MPS) for general spin and particle number invariant fermionic Hamiltonians. This class includes non-relativistic quantum chemical systems within the Born-Oppenheimer approximation. High-accuracy ab ini...

We have implemented the single-site density matrix renormalization group
algorithm for the variational optimization of SU(2) \times U(1) (spin and
particle number) invariant matrix product states for general spin and particle
number symmetric fermionic Hamiltonians. This class also includes
non-relativistic quantum chemical systems within the Born-...

## Projects

Project (1)