# Importance of Accurate Structures for Quantum Chemistry Embedding Methods: Which Strategy Is Better?

journal contribution

posted on 2018-07-03, 00:00 authored by Erik Rosendahl Kjellgren, Jógvan Magnus Haugaard Olsen, Jacob KongstedQuantum
chemistry embedding methods have become a popular approach
to calculate molecular properties of larger systems. In order to account
for finite temperature effects, including both configurational and
conformational averaging, embedding methods are often combined with
molecular dynamics (MD) simulations either in a direct or sequential
manner. One of the decisive factors for a successful application of
embedding methods is that that the underlying structures provided
by the MD simulation are accurate, if not this will result in low-quality
prediction of the molecular properties in question. Here we investigate
different approaches for generating a set of molecular structures
to be used in subsequent embedding calculations ranging from classical
MD using a standard molecular mechanics (MM) force field to combined
quantum mechanics/molecular mechanics (QM/MM) MD. Overall, we find
an intermediate approach relying on classical MD followed by a constrained
QM/MM geometry optimization to be a fairly accurate and very cost-effective
approach, although this procedure naturally leads to underestimation
of, for example, spectral bandwidths.