Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: In search of the ground state crystal structure of Ta$_2$O$_5$ from
  ab-initio and Monte Carlo simulations   Tantalum oxides (Ta$_2$O$_5$) are characterised by attractive physical and
chemical properties, such as high dielectric constants and anti-reflection
behaviour. Recently, Ta$_2$O$_5$ nanoparticles have also been proposed as
possible enhancers of the relative biological effectiveness in hadrontherapy
for cancer treatment. In principle, their electronic properties can be
accurately investigated from first-principles simulations. However, the
existence of several stable polymorphs of these oxides represents a major
difficulty in order to calculate and disentangle their respective spectral
features. To assess this problem, we use linear-response time-dependent density
functional to investigate the energy loss function $\mbox{Im}
(-1/\bar{\epsilon})$, which is a unique fingerprint of the material, in the
optical limit for various polymorphs. We show that the experimental reflection
energy loss signals can be rationalized and interpreted by assuming that the
$\gamma$-phase of Ta$_2$O$_5$ represents the underlying structural model. We
notice that both the inclusion of local field effects and spin-orbit coupling
are crucial to compute the energy loss functions of this material. Finally, to
further validate the $\gamma$-Ta$_2$O$_5$ polymorph as a model for experimental
tantalum oxide, we compute the reflection energy loss spectra using a Monte
Carlo approach, finding an excellent agreement with the experimental data.

36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph