Memoria COMPUTAEX 2019

Memoria Anual 2019
QCT study of the vibrational and translational
role in the H + C2H6(ν 1
, ν 2
, ν 5
, ν 7
, ν 9
and
ν 10
) reactions
Espinosa-Garcia, J., Calle-Cancho, J.,
& Corchado, J. C. (2019). QCT study
of the vibrational and translational role
in the H+ C 2 H 6 (ν 1
, ν 2
, ν 5
, ν 7
, ν 9
and ν 10
)
reactions. Theoretical Chemistry Accounts,
138(10),116. doi: 10.1007/s00214-019-2504-4
Two important issues were analysed in the title
reaction: the effects of vibrational excitation,
associated with mode selectivity, and the role of
translational energy, associated with Polanyi’s
rules. Based on a global analytical potential
energy surface, PES-2018, recently developed
in our group, quasi-classical trajectory (QCT)
calculations were performed at total energy
of 35 kcal mol −1 , either as translation or as
a combination of translation and vibration
energy. Independent vibrational excitation
by one quantum of any of the CH 3
stretching
modes in ethane leads to similar dynamics
pictures of reaction cross sections and H 2
(v′,
j′) rotovibrational and scattering distributions,
ruling out mode selectivity. Normal mode
analysis showed a cold, non-inverted, H 2
(v′)
product vibrational distribution, while
the C 2
H 5
(v′) co-product presented many
vibrational states, all of them with a low
population, practically simulating a classical
behaviour. An equivalent amount of energy
as translation raises reactivity somewhat less
effective than vibrational energy, contrary
to that found for the O( 3 P) + CH 4
reaction.
Both reactions present “central” barriers,
so this opposite behaviour shows the
difficulties for a straightforward application
of the Polanyi′s rules. The role of vibrational
and translational energy on dynamics has
been rationalized by the coupling between
vibrational modes, which makes analysis of
vibrational excitation difficult in polyatomic
systems. Finally, the role of the total energy on
reactivity and mode selectivity was analysed,
concluding that at lower energy, 15 kcal mol −1 ,
translational energy is much more effective
than vibrational energy to enhance reactivity,
while at intermediate energy, 20 kcal mol −1 ,
the situation is more confusing and strongly
dependent on the counting methods used in the
QCT calculations. Therefore, very small mode
selectivity is found, and translation seems
to be more effective in enhancing reactivity
than vibration at low collision energies, while
this behaviour is reversed as we increase the
collision energy, being the turning point around
20 kcal mol −1 .
Photo-sensitizing thin-film ferroelectric
oxides using materials databases and high-throughput
calculations
Plata, J. J., Suárez, J. A., Cuesta-López,
S., Márquez, A. M., & Sanz, J. F. (2019).
Photo-sensitizing thin-film ferroelectric
oxides using materials databases and
high-throughput calculations. Journal of
Materials Chemistry A, 7(48), 27323-27333.
doi: 10.1039/C9TA11820A
Conventional solar cell efficiency is usually
limited by the Shockley–Queisser limit. This
is not the case, however, for ferroelectric
materials, which present spontaneous electric
polarization that is responsible for their bulk
photovoltaic effect. Even so, most ferroelectric
oxides exhibit large band gaps, reducing the
amount of solar energy that can be harvested.
In this work, a high-throughput approach to
tune the electronic properties of thin-film
ferroelectric oxides is presented.
Materials databases were systematically used
to find substrates for the epitaxial growth
of KNbO3 thin films, using topological and
stability filters. Interface models were built
and their electronic and optical properties were
predicted.
Strain and substrate–thin-film band interaction
effects were examined in detail, in order
to understand the interaction between both
materials. We found substrates that significantly
reduce the KNbO3 band gap, maintain KNbO3
polarization, and potentially present the right
band alignment, favoring electron injection in
the substrate/electrode.
This methodology can be easily applied to
other ferroelectric oxides, optimizing their
band gaps and accelerating the development of
new ferroelectric-based solar cells.
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