Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica
Molecular dynamics simulations are used to study structural and dynamic properties of water and aqueous uranyl ion adsorbed in a slit-like pore of amorphous silica. Calculations are performed for the flexible SPC/E water model in the atomistically detailed pores with sizes in the range of 2.0–5.0...
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Інститут фізики конденсованих систем НАН України
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irk-123456789-1181922017-05-30T03:04:00Z Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica Patsahan, T. Holovko, M. Molecular dynamics simulations are used to study structural and dynamic properties of water and aqueous uranyl ion adsorbed in a slit-like pore of amorphous silica. Calculations are performed for the flexible SPC/E water model in the atomistically detailed pores with sizes in the range of 2.0–5.0 nm. The hydroxyl groups on the pore surfaces lead to a strong adsorption and strongly affect the mobility of water molecules. The uranyl ion and its aqueous environment adsorbed in the pores are studied at the room temperature for different amounts of water. The effect of hydroxylated silica pores on the formation of uranyl hydrate complexes is discussed within the present study. Використовуючи метод молекулярної динамiки, дослiджено структурнi та динамiчнi властивостi води i водного розчину iона уранiлу адсорбованих в щiлиноподiбнiй порi аморфного кремнезему. Розрахунки проводилися для випадку гнучкої моделi води SPC/E в атомарно деталiзованiй порi, розмiри якої вибирались в межах 2.0–5.0 нм. Наявнiсть гiдроксильних груп розташованих на поверхнi пори, приводить до сильної адсорбцiї молекул води, що має визначальний вплив на їх динамiку. Детально вивчено випадок iона уранiлу поблизу стiнки пори i вплив гiдроксильних груп на формування його гiдратної оболонки. 2007 Article Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica / T. Patsahan, M. Holovko // Condensed Matter Physics. — 2007. — Т. 10, № 2(50). — С. 143-150. — Бібліогр.: 15 назв. — англ. 1607-324X PACS: 02.70.Ns, 68.43.Jk, 82.70.Gg DOI:10.5488/CMP.10.2.143 http://dspace.nbuv.gov.ua/handle/123456789/118192 en Condensed Matter Physics Інститут фізики конденсованих систем НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| description |
Molecular dynamics simulations are used to study structural and dynamic properties of water and aqueous
uranyl ion adsorbed in a slit-like pore of amorphous silica. Calculations are performed for the flexible SPC/E
water model in the atomistically detailed pores with sizes in the range of 2.0–5.0 nm. The hydroxyl groups on
the pore surfaces lead to a strong adsorption and strongly affect the mobility of water molecules. The uranyl
ion and its aqueous environment adsorbed in the pores are studied at the room temperature for different
amounts of water. The effect of hydroxylated silica pores on the formation of uranyl hydrate complexes is
discussed within the present study. |
| format |
Article |
| author |
Patsahan, T. Holovko, M. |
| spellingShingle |
Patsahan, T. Holovko, M. Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica Condensed Matter Physics |
| author_facet |
Patsahan, T. Holovko, M. |
| author_sort |
Patsahan, T. |
| title |
Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica |
| title_short |
Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica |
| title_full |
Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica |
| title_fullStr |
Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica |
| title_full_unstemmed |
Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica |
| title_sort |
molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica |
| publisher |
Інститут фізики конденсованих систем НАН України |
| publishDate |
2007 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/118192 |
| citation_txt |
Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica / T. Patsahan, M. Holovko // Condensed Matter Physics. — 2007. — Т. 10, № 2(50). — С. 143-150. — Бібліогр.: 15 назв. — англ. |
| series |
Condensed Matter Physics |
| work_keys_str_mv |
AT patsahant moleculardynamicsstudyofaqueousuranylinhydrophilicmesoporousconfinementthecaseofslitlikeporeinamorphoussilica AT holovkom moleculardynamicsstudyofaqueousuranylinhydrophilicmesoporousconfinementthecaseofslitlikeporeinamorphoussilica |
| first_indexed |
2025-07-08T13:32:06Z |
| last_indexed |
2025-07-08T13:32:06Z |
| _version_ |
1837085783401431040 |
| fulltext |
Condensed Matter Physics 2007, Vol. 10, No 2(50), pp. 143–150
Molecular dynamics study of aqueous uranyl in
hydrophilic mesoporous confinement: the case of
slit-like pore in amorphous silica
T.Patsahan, M.Holovko
Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine,
1 Svientsitskii Str., 79011 Lviv, Ukraine
Received March 13, 2007, in final form May 7, 2007
Molecular dynamics simulations are used to study structural and dynamic properties of water and aqueous
uranyl ion adsorbed in a slit-like pore of amorphous silica. Calculations are performed for the flexible SPC/E
water model in the atomistically detailed pores with sizes in the range of 2.0–5.0 nm. The hydroxyl groups on
the pore surfaces lead to a strong adsorption and strongly affect the mobility of water molecules. The uranyl
ion and its aqueous environment adsorbed in the pores are studied at the room temperature for different
amounts of water. The effect of hydroxylated silica pores on the formation of uranyl hydrate complexes is
discussed within the present study.
Key words: molecular dynamics, water, uranyl, confinement, silica
PACS: 02.70.Ns, 68.43.Jk, 82.70.Gg
1. Introduction
Besides the fundamental interest to the radionuclides adsorbed in pores of various materials
based on SiO2 its study turns out to be of great practical importance, especially from the ecological
point of view. The most applied problems considered are aimed at preventing contamination of
large areas caused by radioactive compounds that are capable of migrating through minerals com-
posing the soils and subsurface sediments from the sites where the radionuclides are concentrated:
uranium deposits and uranium ore milling sites, nuclear wastes repositories and sites of nuclear
accidents. Uranium is a major contaminant due to its predominantly heavy metal content of the
spent nuclear fuel. Dissolved uranium dioxide is mostly hexavalent and it can be very mobile in the
water environment depending on the material in which it is confined. The dioxide of hexavalent
uranium is known as uranyl (UO2+
2 ) and it is positively charged. Thus, a coulombic interaction is
very important in such systems. We present the study of some dynamic and structural properties
of uranyl ion and its water environment that are affected by a pore of silica in which they are ad-
sorbed. While one can find numerous experimental results for uranyl ion in various environments,
there are only a few investigations where the uranyl ion interacting with some substrate is consi-
dered using the methods of computer simulations. A molecular dynamics study of aqueous uranyl
near α-quartz surface was presented by Greathouse et al. [1], where a number of radial distribution
functions were obtained for different configurations of uranyl and its hydrate and carbonato com-
plexes. The self-diffusion coefficients of water molecules in different layers relatively to the quartz
surface were calculated. Later, the computer simulations were performed [2,3] in order to study a
sorption of the aqueous uranyl on the clay mineral of montmorillonite. In contrast to the previous
studies where the substrate surface had an ordered structure, we focus on an amorphous structure
since we are interested in the problems concerned with uranyl ion transport and the properties of
its aqueous environment in the so-called lava-like fuel-containing materials formed in the reactor
building of Chornobyl Nuclear Power Plant as a consequence of well known heavy nuclear acci-
dent which happened in 1986. The lava-like fuel-containing materials have a complicated structure
and contain various compounds, but in general they consist of high-radioactive silica glasses. The
c© T.Patsahan, M.Holovko 143
T.Patsahan, M.Holovko
pores in these glasses form a disordered network of meso-scaled channels, where different kinds
of dissolved radionuclides and other light and heavy metals can migrate. Recently, we presented
a study of water dynamics in the model disordered porous material [4]. However, in the current
study we concentrate on the partial case of a confinement, namely on the single-pore model. In
this case we neglect the randomness of porous medium for a better comprehension of structural
and dynamic properties of water and aqueous uranyl in a separate pore. In this way we can try to
better understand different mechanisms of the effect of porous silica on uranyl ion and its aqueous
environment. A slit-like pore model of amorphous silica with atomistically detailed structure is
chosen. The surfaces of pore are saturated by hydroxy groups which appear due to the chemical
reactions of water with non-bonded oxygens on the silica surface. Therefore, the pore is hydrophilic
and the adsorption effects are anticipated. We also consider the cases where hydroxyls are partially
or completely removed from the surfaces. Several widths of meso-pore are studied to demonstrate
a size effect of confinement on the water density profiles and to see how this affects uranyl sorption
dynamics. The average values of self-diffusion coefficients are calculated in the hydrophobic and
hydrophilic pore of 2 nm size.
2. Model and simulation details
The pore is modelled as a space between two slabs of amorphous silica. The space between these
slabs is filled with water molecules of some density. An uranyl ion is involved in the equillibrated
aqueous environment. During the simulation processes the values of (x, y, z)-coordinates of uranyl
ion are stored to analyze its trajectories, while the averaged radial distribution functions, such as
water density profiles and mean-square displacement functions, were produced during simulation
runs. The whole system is atomistically detailed. Therefore, all the pair interactions in the system
can be described in a realistic way, although in this case the simulations are quite time consuming
and cannot be very long-time scaled.
The model of amorphous silica is prepared using molecular dynamics simulations. The β-
cristobalite of SiO2 is chosen as the base atomic structure of silica slab which consists of 5400
atoms and the slab size is about 50 × 43 × 32 Å. The pair interaction between atoms is described
by the Morse potential with the parameters given in [5]. All simulations are performed in the
constant (NVT) ensemble with periodic boundary conditions. Amorphous silica is obtained from
crystalline one following the regime 1-XIII in [5], which includes the heating of crystalline structure
of SiO2 to the temperature of 8000 K and a sequential cooling to the room temperature. After
equilibration of the system at 300 K during 40 ps, the resulting sample is kept at the temperature
of 300 K and at a constant of pressure of 1 atm. The total time of the heating/cooling processes
takes 310 ps. At the final stage, in order to make a silica surface relax, the simulation run of the
prepared structure is performed during 50 ps without periodic boundary conditions in z-direction.
The next step concerns a preparation of silica surface. We remove from the silica surface all
the silicium atoms that are bonded with less than four oxygens like it was proposed in [6,7]. To
saturate the free bonds of non-bridging oxygen atoms (Oh), hydrogens are attached to each Oh at
the distance of 1.0 Å and at the average Si–O–H angle 116◦. In our study the obtained number
density of hydroxy groups on the surface is around 4.9 OH/nm2. This value is in a good agreement
with theoretical and experimental data for amorphous silica [8–10]. Thus, a silica slab is cut off
from the obtained sample. Thereby, two identical silica slabs with thickness of ∼ 15 Å and the
surface area of 48.29×41.82 Å2 are used in order to construct two parallel walls of slit-like pore with
the width of d = 2 nm and boundary conditions in x and y directions. The prepared pore can be
filled with water molecules of corresponding densities. The different densities of water in the pores
are considered. The uranyl ion UO2+
2 is involved in the pore as well. To describe an interaction
between the atoms in the system, the pair potentials and the partial charges are used in accordance
with [1], where the interaction parameters between uranyl ion and water molecules were chosen
following Guilbaud and Wipff [11]. However, in order to provide an electroneutrality in the whole
system the original values of silicon and oxygen atom charges were slightly adjusted. During the
simulation of water and aqueous uranyl ion in the pore, the silica structure remains stationary,
144
Uranyl in hydrophilic mesoporous confinement
e.g. the coordinates of silicium and oxygen atoms are fixed, except for hydrogen atoms in hydroxyl
groups –OH connected with the corresponding non-bridging oxygen atoms by flexible bonds. In
contrast to [1], where the flexible version of SPC model was used as a water model, we prefer a
flexible SPC/E one [12]. We noticed that flexible SPC model gives highly overestimated values for
a self-diffusion coefficient of water molecules, while the self-diffusion coefficient of SPC/E water in
bulk is much closer to the known experimental data (2.3·10−9 m2/s), although being a little bit
lower (2.0·10−9 m2/s). The bonds between uranium and oxygen atoms in UO2+
2 are considered
flexible as well [1]. The snapshot of simulation box with the model system of aqueous uranyl in the
hydrophilic silica pore is presented in figure 1. The potentials and the corresponding parameters
for interatomic interactions are presented in table 1 in [1].
Figure 1. A snapshot of the simulated system. The uranyl ion (in the center) and water in the
slit-like pore of amorphous silica.
To study the density profile of water and its effect on transport phenomena in the pore, different
pore loadings of water molecules are considered. The water density varies in the range of 0.21 −
1.00 g/cm3. Depending on the pore size, the completely loaded pore (1.00 g/cm3) contains 1350,
2024 and 3370 water molecules for the pore sizes of 2, 3 and 5 nm, respectively. The computer
simulations of water and aqueous uranyl in the slit-like pore of silica are performed using the
method of molecular dynamics at a constant temperature T = 300 K in (NVT)-ensemble with two-
dimensional boundary conditions. The equations of motion are integrated with a Verlet leapfrog
algorithm. The interaction cutoff distance 10 Å with long range correction is used. Also the two-
dimensional version of Ewald summation algorithm for electrostatic interactions is applied. The
average values of the desired temperatures were maintained using the algorithm according to the
Nosé-Hoover thermostat with a relaxation time constant t? ∼ 0.1 ps while the simulation time step,
∆t, was set to 0.0005 ps. The time of the system equilibration was 100 ps. During the production
time, 600 ps, the averaged radial distribution functions and the mean-square displacement functions
are calculated. The functions obtained allow us to analyse the structural and dynamic properties
of the components of the system. A random removal of certain number of hydroxyl groups from
the silica surface changes the hydrophilicity of the pore walls. A complete dehydroxylization leads
to the hydrophobicity of the pore due to the absence of polar groups on the surface.
145
T.Patsahan, M.Holovko
3. Results and discussion
Considering various densities of water in the hydrophilic pore, the adsorption effect on the pore
surfaces is distinguished. This effect can be illustrated by the water density profiles in figure 2. The
sharp peaks of the water density profiles indicate that the layering of the water molecules appears
near the pore walls for the water densities of 0.21 g/cm3 and 0.73 g/cm3. Due to hydrophilic
nature of the surface, all water molecules are attracted towards the pore surface. In all cases one
can observe a lower density at the center of pore (z ∼ 0.0) than for bulk water. In the case of a
small amount of water (for example, ρ=0.21 g/cm3) the water molecules can be practically missing
in the pore center.
Figure 2. The water density profiles for differ-
ent pore loadings. The dashed line corresponds
to the case of hydrophobic pore at water den-
sity of ρ = 0.73 g/cm3.
Figure 3. The water density profiles for the
different pore sizes (2–5 nm).
Figure 4. The water density profiles for different pore sizes (2–5 nm) and different surface density
of hydroxyl groups. Dotted lines correspond to the partly hydrated surface of the pores.
In figures 3 and 4 one can see the water density profiles depending on the pore size. If the
pore size is quite large (more than 5 nm), the water molecules in the center of the pore are not
affected by the pore walls and the density profile is uniform in the case of a completely loaded pore.
Therefore, the behavior of the water molecules in this region can be treated in the same way as in
the bulk. When the pore size decreases, the water density is very inhomogeneous and the distance
of the water molecules and the uranyl ion to the wall becomes very important. In this study, two
146
Uranyl in hydrophilic mesoporous confinement
locations of uranyl ion are studied – in the center of the pore and near the pore surface. When
uranyl ion is far from the pore surface, it is not directly affected by hydroxyl groups. However,
when it is near the surface, the binding of uranyl ion and the corresponding hydroxyl can occur.
This binding is accompanied by changes in the hydration shell of the ion. The hydroxyl group
is involved into the hydration shell during the binding process, while one of the five molecules
of hydration shell leaves the ion. The radial distribution functions that illustrate the mentioned
effects are presented in figure 5.
Figure 5. The radial distribution functions U–Ow for the aqueous uranyl and its hydration shell
in a slit-like pore of amorphous silica at the temperature 300 K: (a) uranyl ion in the center of
the pore; (b) uranyl ion near the surface of pore wall.
The density profile of water molecules has a significant effect on the dynamics of the uranyl
ion in the pore. It is noticed that the uranyl ion, placed initially in the pore center, remains in the
central area of the pore during the simulation run and moves together with its hydrate complex in
the XY surface, e.g. along the pore. The hydrate complex has a pentagonal symmetry, the same
symmetry as in the case of uranyl ion in bulk water (figure 5a). The hydrate shell of the uranyl
ion consists of five molecules of water. It was noticed that the binding between the uranyl ion
and the pore wall can appear when the ion is initially placed at the distance of ∼ 2 Å to the
wall. In this case the hydroxyl of silica surface replaces one of the five molecules of water in the
hydrate shell of the uranyl. This phenomenon is illustrated by the corresponding averaged radial
distribution functions and the running coordination numbers in figure 5b. Despite the attraction
between uranyl ion and the pore walls the uranyl ion does not bind with the pore surface by itself
when it is far enough (& 4 Å). This can be explained by the adsorption phenomena that lead to
the formation of a dense layer of water, which resists the penetration of the uranyl ion towards
the wall. In the case of the hydrophobic pore, where the water density is distributed more or less
uniformly in the pore volume (figure 2, dashed line), the uranyl ion easily migrates to the pore
surface and the close vicinity of the uranyl ion to the pore surface reduces its mobility. In all cases
a pentagonal hydrate shell formed at the distance of ∼ 2.51 − 2.52 Å to the center of uranyl ion
is observed. Such a configuration has already been observed in the previous studies by molecular
dynamics simulation [1] as well as by quantum chemistry calculations [13].
When the water density in the pore increases to 1 g/cm3, the uranyl ion initially placed in the
pore center rapidly reaches the pore surface area (figure 6) like it was observed in the hydrophobic
case before. This can be explained by the density profile uniformity along z-direction (figure 4).
However, similar to the previous case, the uranyl ion, being near the pore surface, cannot bind with
hydroxyl group by itself due to its hydration shell that needs some charge redistribution, which
should appear in such complexes. The method of classical molecular dynamics cannot provide any
charge redistribution, because this is a kind of quantum mechanics problem. Thus, some extensions
should be applied to take this effect into account. In our study all the charges are fixed. Therefore,
the whole adsorption process could not be observed in dynamics. However, when the uranyl ion is
147
T.Patsahan, M.Holovko
Figure 6. z-trajectories of uranyl ion in the pores of different sizes and loadings.
placed at the distance ∼ 2−3 Å to the silica surface, it binds easily with a corresponding hydroxyl
group and keeps in its place for a long time during simulation runs (�1000 ps).
In figure 6 one can see a number of z-trajectories of uranyl ion, which is adsorbed in the pores
of different sizes (2–5 nm). It is shown that in the narrow pore (2 nm), the uranyl ion moves fast
towards the pore wall. When the pore increases the averaged velocity of uranyl ion in z-direction
decreases. Moreover, a time delay appears before the ion begins to move to the wall. When the
pore size is of 5 nm, the uranyl ion located in the middle of the pore becomes indifferent to the
pore walls. Moving around, the uranyl ion can approach one of the walls, but the time needed to
do that is much longer – more than a few orders of magnitude larger than in the case of 2 nm and
3 nm. A tendency to the motion of the ion towards the wall was not observed even after 1000 ps.
Figure 7. The mean-square displacement functions and the total self-diffusion coefficients of wa-
ter molecules in the slit-like pore of amorphous silica for different levels of the pore hydrophilicity.
The pore size is equal to 2 nm.
Thus, we should determine the effect of the pore hydrophilicity on the water dynamics, the
averaged values of the total self-diffusion coefficient of the water molecules in the pore of 2 nm and
the different surface densities of hydroxyl groups. For this purpose the functions of mean-square
displacement (MSD) are calculated (figure 7). The three values of the surface densities of hydroxyls
are chosen, that correspond to the full hydroxylated surface (100% or 4.9 OH/nm2 for the system
considered), partial hydroxylated (2.5 OH/nm2) and completely dehydroxylated surface (0%). The
self-diffusion increase is observed when the surface density of hydroxyls decreases. The dashed lines
denote MSD functions in z-direction. This particular form of the MSD functions is appropriate to
the case of the molecular dynamics in confined space, where the motion in some directions is
148
Uranyl in hydrophilic mesoporous confinement
restricted by the pore walls and the maximum value of the MSD function – which is reached in
this case – defined by a pore size. The calculated values of the self-diffusion coefficient are close to
that predicted in [14,15] for water adsorbed in Vycor-like glass at the similar conditions.
4. Conclusions
The model of a slit like pore of silica is considered within this study. The water density profiles
are obtained to study an effect of the pore size and its loadings on the uranyl ion dynamics. If the
pore is narrow (2–3 nm) and the loading is close to 1 g/cm3 of the water density, the uranyl ion
adsorbs very fast on the pore surface. In the hydrophobic pore the uranyl ion reaches the surface of
a partly loaded pore faster than in the hydrophilic one. However, in the hydrophobic pore, where
hydroxyl groups are absent, the ion cannot associate with the surface.
The significant effect of the arrangement of the water molecules in the pore on the uranyl ion
behavior and its hydration shell inspired us to consider them depending on the pore parameters.
The layering structure of the density of water molecules near the pore surface is observed in the
hydrophilic pore. The first peak in the water density profile becomes lower when the surface density
of hydroxyls decreases. Moreover, the water density distribution through the pore volume is more
homogeneous when there is a small amount of the hydroxyl groups on the surface. In the case
of partially loaded pore, the water molecules are practically missing in the center of the pore .
When the pore surface is hydrophobic (small amount of hydroxyl groups), the difference between
the densities of water molecules in the center and near the surface of the pore is much smaller. In
the pore that is partially loaded with water molecules, one can see a high inhomogeneity of water
density which is caused by adsorption of water molecules on the hydrophilic pore surface. Due to
a small amount of water that is incapable of filling the whole pore, one can notice an asymmetry
in the water density profile. An asymmetric profile indicates that the most part of water molecules
prefers one of the two pore walls in the time interval observed. In the case of a pore completely
loaded with water molecules (ρ = 1 g/cm3), the average self-diffusion coefficient of water decreases
when the surface density of hydroxyl groups increases.
The aqueous uranyl ions confined in the silica pore are attracted to the pore walls and bind
with the silica surface. Due to a strong association, the uranyl ion remains on the silica surface for a
long time. A reverse process (e.g. disconnection of uranyl ion) was not observed during simulation
runs (> 600 ps). Near the silica surface, the hydrate shell of uranyl ion consists of four water
molecules and one hydroxyl group bearing on the surface. A complex of four water molecules and
one hydroxyl group was obtained only when uranyl ion was placed at the distance of ∼ 2 Å from
the silica surface.
The report presented here is only preliminary and should be extended and perhaps studied
more in detail in some directions. However, the obtained results give us a flavor of the structure as
well as show the dynamics of the system considered. The problems that emerged during this study
suggest us to make some modifications related to the model of the system as well as to the very
simulation process. The first methodical problem concerns the charge redistributions during the
binding processes of uranyl ion and water/hydroxyl that should be taken into account in order to
correctly describe the adsorption process. Another problem consists in the large time consumption
while simulating the dynamics in such systems. Being a very heavy compound compared to water
molecules, the uranyl ion has an extremely slow dynamics that cannot be observed properly during
relatively short-time scale simulations (∼ 1000 ps) within the framework of the model considered
in this study. Therefore, a more simple model of silica structure is needed, where the number of
sites of interaction are much less.
5. Acknowledgements
TP thanks the World Federation of Scientists and ICSC “World Laboratory” for the partial
financial support within the framework of the National Scholarship Program. The computational
facilities were provided by the computing cluster of the Institute for Condensed Matter Physics.
149
T.Patsahan, M.Holovko
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Молекулярна динамiка водного розчину уранiлу в
гiдрофiльнiй нанопорi: випадок щiлиноподiбної пори
аморфного кремнезему
Т.Пацаган, М.Головко
Iнститут фiзики конденсованих систем НАН України, вул. Свєнцiцького, 1, 79011 Львiв, Україна
Отримано 13 березня 2007 р., в остаточному виглядi – 7 травня 2007 р.
Використовуючи метод молекулярної динамiки, дослiджено структурнi та динамiчнi властивостi во-
ди i водного розчину iона уранiлу адсорбованих в щiлиноподiбнiй порi аморфного кремнезему. Роз-
рахунки проводилися для випадку гнучкої моделi води SPC/E в атомарно деталiзованiй порi, розмiри
якої вибирались в межах 2.0–5.0 нм. Наявнiсть гiдроксильних груп розташованих на поверхнi пори,
приводить до сильної адсорбцiї молекул води, що має визначальний вплив на їх динамiку. Детально
вивчено випадок iона уранiлу поблизу стiнки пори i вплив гiдроксильних груп на формування його
гiдратної оболонки.
Ключовi слова: молекулярна динамiка, вода, уранiл, обмежений об’єм, кремнезем
PACS: 02.70.Ns, 68.43.Jk, 82.70.Gg
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