Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fixed and partial-node approximations in Slater determinant space for
  molecules   We present a study of fixed and partial-node approximations in Slater
determinant basis sets, using full configuration interaction quantum Monte
Carlo (FCIQMC) to perform sampling. Walker annihilation in the FCIQMC method
allows partial-node simulations to be performed, relaxing the nodal constraint
to converge to the FCI solution. This is applied to ab initio molecular
systems, using symmetry-projected Jastrow mean-field wave functions for
complete active space (CAS) problems. Convergence and the sign problem within
the partial-node approximation are studied, which is shown to eventually be
limited in its use due to the large walker populations required. However the
fixed-node approximation results in an accurate and practical method. We apply
these approaches to various molecular systems and active spaces, including
ferrocene and acenes. This also provides a test of symmetry-projected Jastrow
mean-field wave functions in variational Monte Carlo (VMC) for a new set of
problems. For trans-polyacetylene molecules and acenes we find that the time to
perform a constant number of fixed-node FCIQMC iterations scales as O(N^{1.44})
and O(N^{1.75}) respectively, resulting in an efficient method for CAS-based
problems that can be applied accurately to large active spaces.

16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga