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Journal of Physics: Conference Series
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PAPER • OPEN ACCESS
Density-functional approximations on CO2@sI
clathrate hydrate interactions
To cite this article: Daniel J. Arismendi-Arrieta et al 2017 J. Phys.: Conf. Ser. 875 112015
View the article online for updates and enhancements.
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This content was downloaded from IP address 80.82.77.83 on 25/10/2017 at 17:13
ICPEAC2017
IOP Conf. Series: Journal of Physics: Conf. Series 1234567890
875 (2017) 112015
IOP Publishing
doi:10.1088/1742-6596/875/12/112015
Density-functional approximations on CO2 @sI clathrate hydrate interactions
Daniel J. Arismendi-Arrieta∗1, Álvaro Valdés†2, Rita Prosmiti ∗3
†
∗ Institute of Fundamental Physics (IFF-CSIC), CSIC, Serrano 123, 28006 Madrid, Spain
Departamento de Física, Universidad Nacional de Colombia, Calle 26, Cra 39, Edificio 404, Bogotá, Colombia
Synopsis Clathrate hydrates have unique physical and chemical properties and considering that the stability of such systems is
strongly related with its guest. In the last decades a renewed interest on these substances have grown up due to their potential
industrial applications, with gas hydrate research becoming a joint field of various engineering disciplines and fundamental
sciences.
5
12
12 2
5 6
}
Interaction energies
1) Reference data
2) Error analysis
a) Equilibrium geometries
b) Scan z−axis curves
c) Correlation plots
VALIDATION PROTOCOL
Such facts, motivated us to evaluate the description of the guest-host CO2 @sI clathrate hydrate interactions from wave-function (WFT) and density
function theory (DFT) electronic structure calculations. Computed couple-cluster or MP2 reference interaction energies for a representative set of configurations are used to assess the accuracy of modern
DFT approximations (empirical and nonempirical),
including the effect of semilocal approach, exactexchange/correlation admixture, range-separation, as
well as dispersion-correction terms [2]. In this work,
results are presented for the T and D cages of the
CO2 @sI clathrate hydrate (see Figure 1) obtained
from twelve functionals available or recently implemented in Gaussian package [3]. Each density functional approximation (DFA) was evaluated following a protocol of complementary strategies [4] (see
Figure 1). First, an extended benchmark dataset
was introduced by performing reference explicitly
correlated CCSD(T)-F12/DF-MP2 calculations, and
sampling configurations in near-equilibrium and rep-
resentative stretched regions of the potential; not,
as traditionally, only equilibrium configurations. In
turn, error analysis was carried out for each DFA
for both the minimum interaction energies, as well
as the remaining set of energies, following by scans
of the potential along relevant orientations, complemented by correlation plots for a complete exploration of the systems configurational space. Finally,
comparisons with semiempirical, as well as ab initiobased effective pairwise models commonly used as
a first approximation in molecular simulations, indicate that for microscopic considerations on the interactions further refinements in such analytical representations should be incorporated in these analytical
representations.
CO2 @sI building blocks
So far, clathrate hydrates have attracted the interest of both experimentalists and theorists [1], focused mainly on two fundamental problems, a) at
which conditions (pressure, temperature, concentration) gas hydrate may be formed or decomposed, and
b) what structure type of gas hydrate could be obtained at these conditions. Although many characteristics of clathrate hydrates are well known experimentally, other relevant to microscopic aspects, such
as accurate estimations through modelling is a scientific challenge. Related with this, computational simulations have been usually limited by the accuracy
of the models in describing guest-host interactions,
while currently first-principles and ab initio calculations are being used to determine molecular scale
parameters (interaction force-fields, structural variables, spectra), that are essential for understanding
fundamental aspects of hydrate formation, stability
and thermodynamics.
DFT/DFT−D vs Accurate Methods
Figure 1. Protocol used to validate the performance of
different DFAs with and without dispersion corrections
for the sI building blocks, CO2 (H2 O)20,24 , interactions.
References
[1] E. D. Sloan et al. 2007 Clathrate Hydrates of Natural
Gases CRC Press 3rd Edition
[2] M.G. Medvedev et al. 2017 Science 355 49
[3] M.J. Frisch et al. 2016 Gaussian 09; 2004 Gaussian
03 Gaussian, Inc., Wallingford CT.
[4] D. J. Arismendi-Arrieta et al. 2017 to be submitted
1 E-mail:
d.arismendi@iff.csic.es
2 E-mail: avaldesl@unal.edu.co
3 E-mail: rita@iff.csic.es
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd
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