Formation of Trilayer Ices in Graphene Nanocapillaries under High

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Formation of Trilayer Ices in Graphene Nanocapillaries under High Lateral Pressure YinBo Zhu, Feng-Chao Wang, Jaeil Bai , Xiao Cheng Zeng, and Heng-An Wu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b00258 • Publication Date (Web): 01 Apr 2016 Downloaded from http://pubs.acs.org on April 4, 2016

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The Journal of Physical Chemistry

Formation of Trilayer Ices in Graphene Nanocapillaries under High Lateral Pressure

YinBo Zhu1, FengChao Wang1*, Jaeil Bai2, Xiao Cheng Zeng2,3*, HengAn Wu1 1

CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department

of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China 2

Department of Chemistry, University of Nebraska-Lincoln, NE 68588, USA

3

Hefei National Laboratory for Physical Sciences at Microscale and Collaborative

Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, Anhui 230026, China

Abstract Using molecular dynamics simulation, we investigate phase behavior of water confined in graphene nanocapillaries at the room temperature (300 K). Here, the lateral pressure Pzz is used as the primary controlling variable and its effect on the behavior of trilayer water is systematically studied. Three (meta)stable trilayer (TL) crystalline/amorphous ice phases, namely, TL-ABAI, TL-ABA, and TL-AAAI, are observed in our simulations with the lateral pressure in the range of 1.0 GPa ≤ Pzz ≤ 6.0 GPa. The TL-ABAI exhibits a square lattice in every layer and the three layers exhibit the ABA stacking pattern, i.e., the oxygen atoms in the two outer layers are in registry. This new trilayer ice structure can be also viewed as bilayer clathrate hydrate with water molecules the middle layer serving as the guest molecules. With increasing the lateral pressure, typically, the solid-to-liquid-to-solid phase transition occurs, during which the structural transformation from triangle to square-like in the ice layer is accompanied with a sudden jump in P⊥ (normal pressure) and in potential energy (per molecule). The oxygen density profiles of the three trilayer structures show a 1

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common feature, that is, the peak of the middle layer is markedly lower than that of two outer layers. The computed diffusivity suggests that water in the middle layer exhibits different behavior from that in the two outer layers in contact with the graphene. For TL-AAAI, the diffusion of water molecules in the layer next to the graphene is faster than those in the middle layer.

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Introduction The phase behavior of water continues to be a subject of extensive research interests due to its intriguing properties and strong relevance to numerous scientific disciplines. At ambient pressure, unconstrained bulk water typically exhibits vapor, liquid, and solid (ice Ih) phases, depending on the temperature. However, in constrained high-pressure environment, water can form new solid phases not seen in the open air. The special feature of confined water stems not only from intrinsic hydrogen-bonding network but also from inhomogeneity of the confined liquid, particularly in the nanoscale confinement. Notable aspects include a wealth of crystalline/amorphous two-dimensional (2D) phases and metastable phases in the compression limit of liquid water.1-7 A better understanding of the effects of confinement and lateral pressure on the phase behavior of water will further the advancement of water physics such as the phase diagram of low-dimensional water. Previous studies have shown that water/ice in carbon nanotubes or slit pores exhibits various new solid structures.5-26 The spontaneous formation of 2D bilayer hexagonal ice was first predicted by Koga et al. through molecular dynamics (MD) simulation.10 Numerous low-dimensional ice polymorphs have been revealed from MD simulations, experiments or from both, such as 1D ice nanotubes,8,9,13,14 2D monolayer,4-7,11,12,15,16 bilayer,4-7,10,16,17 and trilayer ice4-7,18-21 polymorphs. Bai et al. and Takaiwa et al. investigated different phases of 1D ice versus diameter of carbon nanotube and axial pressure.8,9 The main focus of the present simulation study is the phase behavior 2D trilayer ices. Note that several trilayer ice structures have been predicted to form between hydrophobic plates from MD simulations.5,18-21,27 In particular Giovambattista et al. showed that the middle water layer can behave quite differently from the two outer layers next to the slit walls. Interestingly, the trilayer water is characterized by a middle liquid-like layer sandwiched between two crystal-like layers.18 Kumar et al. simulated a trilayer ice in which the two outer layers are flat while the middle layer is puckered.20 Planar and puckered trilayer ices were also found by Kastelowitz et al.19 3



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Zangi and Mark investigated the freezing of confined water between two parallel plates under the inﬂuence of a uniform external electric ﬁeld in the lateral direction.26 Two trilayer ice and amorphous ice with the AAA and ABA stacking in the graphene capillary were reported by us recently.7 In a recent experiment study, Algara-Siller et al. demonstrated that when water is constrained between two sheets of graphene, the 2D liquid water can turn into a monolayer ice with square pattern under the high lateral pressure.6 Both experimental and simulation results suggest that the vdW pressure is on the order of GPa magnitude.6,28 In the graphene nanocapillaries, the high vdW pressure is key to the spontaneous formation of high-density monolayer square ice structure.6 Some recent simulation and first-principles studies also show rich 2D crystalline and amorphous phases of water confined in graphene nanocapillaries.29-33 These studies mainly report the monolayer square ice and the stacking order of bilayer ice. To our knowledge, a comprehensive simulation study of trilayer crystalline/amorphous phases and associated solid-to-liquid-to-solid phase transitions for water confined in graphene nanocapillaries is still lacking. Building upon our recent computational investigations of compression-limit phase behavior under nanoscale graphene confinement,6,7 we report a new trilayer ice structure, namely, the trilayer square ice with ABA stacking order (with square lattice in every layer). Particular attention is also placed the relationship between this new trilayer structure with the other two trilayer ice structures reported previously.7 We find that the middle layer in the trilayer ice/amorphous ice is quite different from the two outer layers in direct contact with the graphene.18

Computation Methods We perform molecular dynamics (MD) simulations of trilayer water confined in graphene nanocapillaries, using the LAMMPS program.34 Our simulation system is similar to that used in previous studies,6,7 in which two water reservoirs contain 1000 water molecules each were connected by the nanocapillary consisting of two parallel graphene sheets. The lateral pressure pushes water molecules in reservoirs into a 4


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graphene nanocapillary. The length and width of the graphene nanocapillary are fixed at 42.60 Å and 36.89 Å, respectively, in all simulations. The distance h between the center plane of the graphene wall is fixed at 9.0 Å, 10.0 Å and 11.5 Å for the three different trilayer structures, respectively. Periodic boundary conditions are imposed on all three directions. The MD simulations are performed in the isothermal-isobaric (NPzzT) ensemble, in which the temperature (T = 300 K) and lateral pressure (Pzz) are controlled by the Nosé-Hoover thermostat and barostat, respectively. The total number of water molecules N in the nanocapillary can change, depending on Pzz and h. A time step of 1.0 fs is used for the velocity-Verlet integrator. The pairwise interactions between any two water molecules are described by the extended four-point charge (TIP4P/2005) model,35 including the long-ranged Coulomb potential and the short-ranged Lennard-Jones (LJ) 12-6 potential between the interaction sites. The long-range Coulombic interaction is calculated using a particle-particle particle-mesh (PPPM) algorithm with an accuracy of 10-4. The interaction between water molecules and the graphene wall is Σ ϕwall(ri, rj), where ri stands for the coordinate of water molecule i, ϕwall is the Lennard-Jones potential for water-graphene interaction.7,9 The cutoff distance for the LJ interaction is set to be 12.0 Å,38 and 8.5 Å for Coulombic interaction. The distance from oxygen atom to the massless charge site dOM = 0.1546 Å. The water LJ potential interaction parameters are as follow: σOO = 3.1589 Å, εOO= 0.1852 kcal/mol, σOH =0, εOH=0, σHH =0, and εHH=0.39 The carbon-carbon interaction parameters σCC =3.2211 Å and εCC=0.0474 kcal/mol.7, 40

Results and Discussions Phase transition in the compression limit can be observed in the MD simulation at different Pzz and h. For the formation of the trilayer crystalline or amorphous ice phases, the ABA stacking order structure tends to form in relatively narrow graphene nanocapillaries, whereas the AAA stacking order structure tends to form in relatively wide nanocapillaries.7 Our extensive MD simulations give rise to three trilayer ice 5



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structures. In Figure 1(a-c), the blue, green and red colors are used to highlight three different layers of the trilayer ices. Figure 1(d-f) and 1(g-i) display the oxygen-oxygen radial distribution functions (gO-O(r)) and oxygen density profiles of the three trilayer structures, respectively. A new crystalline trilayer ice structure with the ABA stacking order (TL-ABAI) is shown in Figure 1(a). The other two trilayer ices, i.e., the trilayer amorphous ice with the ABA stacking pattern (TL-ABA) [Figure 1(b)] and the trilayer ice with the AAA stacking pattern (TL-AAAI) [Figure 1(c)], have been reported previously.7

Figure 1. Three trilayer ice/amorphous ice structures observed in the MD simulations. (a) A typical snapshot of the TL-ABAI at h = 9 Å, Pzz = 5.5 GPa and T = 300 K. (b) A typical snapshot of TL-ABA at h = 10.0 Å, Pzz = 5.0 GPa and T = 300 K. (c) A typical snapshot of TL-AAAI at h = 11.5 Å, Pzz = 2.5 GPa and T = 300 K. For the three trilayer ice/amorphous ice structures, the blue, green and red water molecules denote the three different ice layers in the graphene nanocapillary. (d-f) Oxygen-oxygen radial distribution functions for the three trilayer structures. The three insets show the zoomed trilayer structures. (g-i) Oxygen density profiles along y axis (normal to the 6


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graphene) for the three trilayer structures. The inset in (g) shows the color code for the three ice layers for the trilayer structures.

The TL-ABAI [Figure 1(a)] is an inerratic structure, which can be transformed from the bilayer AA stacking ice under high lateral pressures (Supporting Information Movie S1). Its structure differs from that of the TL-ABA amorphous and TL-AAAI. In TL-ABAI, the third layer (red color) is in registry with the first layer (blue color) while the second (or middle) layer (green color) is staggered with both the first and third layer. Every four water molecules form an inerratic square in every single layer. Each water molecule in the middle layer is located in the center of a square prism formed by eight water molecules in the first and third layers. The gO-O(r) shown in Figure 1(d) confirms that the TL-ABAI is a crystalline phase, which exhibits the first high peak at 2.79 Å and followed by several relatively high peaks at distance of multiples of ~2.79 Å. The lattice constant of the three trilayer ices is 2.79 ± 0.06 Å, consistent with the experimental result of Ref. 6. The oxygen density profile in Figure 1(g) shows that TL-ABAI is a high-density ice, with density higher than that of TL-AAAI but close to TL-ABA. More structural detail of the TL-ABAI is illustrated in Figure 2 and Figure S1. A typical snapshot of the hydrogen-bonding network [Figure 2(a)] shows that water molecules in the middle layer form hydrogen bonds with adjacent layers. The TL-ABAI structure can be viewed as a bilayer clathrate hydrate with water molecules the middle layer viewed as the guest molecules. Figure 2(b) displays this special clathrate-like structure. Every four blue water molecules are superimposed on top of another four red water molecules, which form a cube-like structure. Every green water molecule is located at the center of this cube. Water 7



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molecules in the first layer and third layer are connected with the middle layer through hydrogen bonds [see Figure 2(b)].

Figure 2. (a) Hydrogen-bonding network of the TL-ABAI at h = 9 Å. Blue, green and red water molecules denote three different ice layers, respectively. (b) An illustration of the clathrate-like structure (shown in the green dash-line box). (c) Oxygen atoms in TL-ABAI, which show an ordered arrangement. (d) The top layer of TL-ABAI. (e) The middle layer of TL-ABAI. Red and white balls represent the oxygen atoms and hydrogen atoms, respectively. The water molecules in every layer exhibit square lattice structure.

Similarly, the TL-ABA amorphous ice [Figure 1(b)] can be also viewed as a clathrate-like structure. The main difference between TL-ABAI and TL-ABA is the oxygen configuration, which is square for TL-ABAI [Figure 2(c)] but rhombic for TL-ABA. The three layers in the TL-ABAI structure are composed of squares (Figure 2 and Figure S1). Although the square lattice can be formed in every layer, it cannot form a perfect hydrogen-bonding network like the monolayer square ice because some hydrogen atoms in one layer form hydrogen bonds with oxygen atoms in the adjacent layer. Note that water molecules in the middle layer (green color, Figure S1(b)) are loosely connected with each other. Hence, they have to be bonded with water molecules in adjacent layers. Some transient solid structures are observed in the MD simulation at h = 11.5 Å, 8


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e.g., during transformation of TL-AAAI to a four-layer amorphous ice with the ABAB stacking pattern (Movie S2) at high lateral pressures. As shown in Figure S2, in the transient structure TL-AAB, the middle layer (green color) is in registry with the first layer (blue color) while the third layer (red color) is staggered with both the first and middle layer. The oxygen density profile of TL-AAB [Figure S2(c)] indicates that the middle layer is puckered but its structural feature differs from that of the trilayer ice reported in Kumar et al.20 The puckered middle layer does not have a clear zigzag configuration like puckered monolayer ice. As such, the transient structures look more disordered than TL-AAAI. The water molecules in every layer of TL-AAB form a triangular lattice (Figure S3). However, this transient structure can only last for a few ns. The mean-squared-displacement (MSD) result [Figure S2(e); 20 ns] shows that the slope of the MSD curve increases first and then levels off, indicating the TL-AAB changes to another structure. Indeed, at the high lateral pressure, the TL-AAB turns into another transient structure [see the inset in Figure S2(e)] similar to the trilayer ice reported in Kumar et al.20 Ultimately, the TL-AAAI turns into the four-layer amorphous ice. The solid-to-liquid-to-solid phase transition with increasing the lateral pressure starts from the bilayer triangular ice with AA stacking (BL-AAI) to the TL-ABAI, and it is associated with a sudden change in potential energy per molecule (Figure 3(a)). Three regions in Figure 3(a) correspond to the BL-AAI, an intermediate liquid phase, and the TL-ABAI. Similarly, from the TL-AAAI to the four-layer ice, the potential energy per molecule exhibits a suddenly jump at ~4.2 GPa [Figure 3(b)]. The five regions in Figure 3(b) correspond to a liquid phase at low pressure, TL-AAAI, trilayer amorphous with puckered middle layer, an intermediate liquid state at high pressure, and the four-layer amorphous ice with the ABAB stacking, respectively. The insets display the structural features and oxygen density profiles for every region. The TL-AAAI exhibits a triangular structure while the four-layer amorphous ice with the ABAB stacking exhibits square-like configuration (see Figure S4). Another relatively long-time simulation (40 ns, from 2.5 GPa to 4.5 GPa; see Figure S5) shows that the trilayer structure with puckered middle layer differs from either TL-AAAI or 9



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TL-ABAI. The puckered middle layer is unstable, making the transient trilayer structures look more stagger. The slope of the MSD curve indicates that the diffusion coefficient of water molecules in the TL-ABAI is less than that in TL-AAAI.

Figure 3. (a) Solid-to-liquid-to-solid phase transition from the bilayer triangular ice BL-AAI to TL-ABAI at h = 9 Å. Potential energy per molecule and the number of water molecules in the nanocapillary exhibit a sudden increase with increasing the lateral pressure (4~6 GPa). (b) Compression limit of a trilayer liquid water constrained in graphene nanocapillary at h = 11.5 Å, T = 300 K and 1.0 GPa ≤ Pzz ≤ 6.0 GPa. The five regions correspond to a liquid phase, TL-AAAI, the trilayer amorphous ice with puckered middle layer, an intermediate liquid state, and the four-layer amorphous ice with ABAB stacking, respectively.

Note that in both cases of the solid-to-liquid-to-solid transition, the Oswald staging phenomenon occurs, namely, an intermediate liquid state becomes stable within a range of pressures in between those of the two ice phases [see Figure 4(a-b), Movies S1 and S2]. The Oswald staging phenomenon for 2D ices was previously observed by us.4,36 Figure 4(a) and 4(b) shows that the structural transformation from triangle to square-like is associated with a sudden increase in P ⊥ (the pressure perpendicular to the graphene) in the intermediate liquid state, due to one more layer of water enters into the channel. Figure 4(c) and 4(d) illustrates the oxygen-oxygen radial distribution function in different pressure regions. The black solid lines represent the intermediate liquid state, which clearly do not show long-range order. In Figure 4(c), the gO-O(r)s of BL-AAI and TL-ABAI exhibit sharp peaks (e.g., a high peak at ~2.79 Å, followed by several low peaks), whereas the gO-O(r) of the liquid state only shows two low and broad peaks. Figure 4(d) displays similar features as Figure 4(c), where the variation of gO-O(r)s indicates that an intermediate liquid state 10


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arises.

Figure 4. (a) Pressure perpendicular to the graphene (P⊥) versus the lateral pressure in the solid-to-liquid-to-solid transition from BL-AAI to TL-ABAI (h = 9 Å, T = 300 K). (b) P⊥ as a function of lateral pressure in the solid-to-liquid-to-solid transition from trilayer ice to four-layer ice (h = 11.5 Å, T = 300 K). (c) and (d) Oxygen-oxygen radial distribution function in three different pressure regions.

Note that for all three trilayer crystalline and amorphous ices found in our simulations, the oxygen density peak [Figure 1(g-i)] of the middle layer is lower than those of the two layers in contact with the graphene. However, from Figure 1(a-c), we can see that the number of water molecules in the three layers is about the same. The oxygen density profiles [Figure 1(g-i)] of the three trilayer structures also show that the width of middle layer is wider. Hence, the middle layer is expected to behave differently from the other two layers, even all three layers exhibit similar square or rhombic structure. To further understand the structural differences among the three trilayer crystalline/amorphous ices, the MSD for water molecules in each layer and the whole ice structure are illustrated in Figures 5 and 6. The slope of the MSD versus time is proportional to the diffusion coefficient of the water molecules. Considering the hydrogen atoms in the channel cannot be divided into layer conveniently, we only calculate the MSD of oxygen atoms in each layer. 11



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Figure 5(a-c) displays the MSD curves for each layer perpendicular to the graphene (MSD ⊥ ), while Figure 5(d-f) displays the MSD curves for each layer parallel to the graphene (MSD||). The blue, green and red lines represent the MSD of oxygen atoms in each layer of the three layers in the channel, respectively. For all three trilayer structures, the MSD of the first layer (blue) and third layer (red) is essentially the same. Whereas the MSD of the middle layer (green) is notably different from those of the other two layers. As shown in Figure 5(a) and 5(d), the MSD⊥ and MSD|| of TL-ABAI show a step-like change and then level off. The step-like changes are closely correlated for the three layers, and these changes are mainly due to vacancies (Figure S6) in the TL-ABAI. The migration of the vacancies results in sudden jump in MSD⊥ and MSD||. When the vacancies disappear in the channel (Figure S6), MSD levels off. Both MSD⊥ and MSD|| of the center layer are higher than those of the other two layers. The numerical value of MSD is very small, reflecting that the TL-ABAI is a solid. For TL-ABA, the MSD⊥ [Figure 5(b)] of middle layer is a bit larger, compared to the other two layers, while the MSD|| [Figure 5(e)] of the three layers is nearly the same. For TL-AAAI, unlike other two trilayer structures, the MSD|| of the middle layer is lower than that of the other two layers. The slope of the three MSD|| lines suggests that water molecules in the two layers in contact with the graphene move faster. This diffusion behavior of molecules close to the surface, and away from the surface resembles that of simple liquids.20,37

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Figure 5. Computed mean-squared displacement (MSD) for oxygen atoms in the three layers in graphene channel for the three trilayer crystalline/amorphous ices. The blue, green and red lines represent the MSD of molecules in each of the three layers, respectively. (a-c) The MSD for water molecules moving in the direction perpendicular to graphene (MSD⊥). (d-f) The MSD for water molecules moving in the direction parallel to graphene (MSD||).

Figure 6 displays the MSD (20ns) curves of the three trilayer structures. The slope of the curve for TL-ABAI and TL-ABA is nearly close to zero, indicating that the ABA stacking ice is in solid state. The MSD curve of the TL-AAAI exhibits a higher slope. The slope of the MSD for TL-AAAI in Figure 6 is not zero, due to that 300 K is a relatively high temperature (close to the melting point of for TL-AAAI). Computed MSD curves of the TL-AAAI at 240 K and 280 K are shown in Figure S7, which indicate that the TL-AAAI is truly in a solid state. Moreover, the diffusivity of TL-AAAI is several orders of magnitude lower than that (5.4 × 10-5 cm2/s) of bulk water under 2 GPa pressure.

Figure 6. MSD of three trilayer structures. The slope of the MSD curve versus time is proportional to the diffusion coefficient. The red, black, and blue circles represent the MSD of TL-ABAI, TL-ABA, and TL-AAAI, respectively.

The MSD results show that the middle layer is different from the other two layers in contact with the graphene. For all three trilayer structures, the MSD⊥ for the middle layer is higher than those of the two layers next to the graphene, indicating that the vibration of water molecules in the middle layer in the direction perpendicular to graphene is stronger than that in the other two layers. It is also correlated with 13



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oxygen density profiles in Figure 1(g-i), where the width of the middle layer is wider. Compared to TL-AAAI, the three MSD|| curves [Figures. 5(d) and 5(e)], corresponding to the three layers, are closer to one another for both TL-ABAI and TL-ABA. This might be due to the high density ABA stacking structure at high pressure. The MSD|| of TL-AAAI [Figure 5(f)] shows that the water molecules in the layer next to the graphene move faster than water molecules in the middle layer. The MSD results of each layer of the three layers show a synchronous feature, reflecting that there are abundant of hydrogen bonds between the adjacent layers. The motion of each single layer is interactive and correlative.

Conclusion In conclusion, three trilayer ices/amorphous ices are observed in MD simulations for trilayer water constrained in graphene nanocapillaries. The TL-ABAI is a clathrate-like inerratic structure with square lattice pattern in every layer. With increasing the lateral pressure, the solid-to-liquid-to-solid phase transition typically occurs during which structural transformation from triangle to square-like is accompanied with a sudden jump both in P⊥ and potential energy per molecule. For all three trilayer structures, the oxygen density profiles show that the peak of the middle layer is lower than those of the other two layers while the width of the middle layer is wider. The MSD data show that the middle layer is quite different from the other two layers in that the vibration of water molecules in the middle layer is stronger than that in the other two layers. The abundant of hydrogen bonds between the adjacent layers render the motion of the three layers interactive and correlative. Lastly, in the TL-AAAI, water molecules in the layer next to graphene move faster than in the middle layer.

Acknowledgements. This work was jointly supported by National Natural Science Foundation of China (11525211, 11472263, 11572307), Anhui Provincial Natural Science Foundation (1408085J08), the Fundamental Research Funds for the Central 14


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Universities of China, and USTC Qian-ren B (1000-Talents B) fund for summer research. Supporting Information Available: Movies of solid-to-liquid-to-solid phase transition from bilayer ice to trilayer ice (Movie S1) and from trilayer ice to four-layer ice (Movie S2). More structural details of TL-ABAI (Figure S1), TL-AAB (Figures S2 and S3) and four-layer amorphous ice with the ABAB stacking (Figure S4); relatively long-time simulation (40 ns, from 2.5 GPa to 4.5 GPa) for compression limit of trilayer ice (Figure S5); the migration of vacancy defect in TL-ABAI (Figure S6); and the computed MSD curves of the TL-AAAI at different system temperatures (Figure S7). These materials are free of charges.

Corresponding Authors [email protected]; [email protected] References 1.

Poole, P. H.; Sciortino, F.; Essmann, U.; Stanley, H. E. Phase Behaviour of Metastable Water. Nature. 1992, 360, 324-328.

2.

Sciortino, F.; Essmann, U.; Stanley, H. E.; Hemmati, M.; Shao, J.; Wolf, G. H.; Angell, C. A. Crystal Stability Limits at Positive and Negative Pressure and Crystal-to-Glass Transitions. Physical Review E, 1995, 52, 6484-6491.

3.

Debenedetti, P. G.; Stanley, H. E. Supercooled and Glassy Water. Physics Today, 2003, 56, 40-46.

4.

Bai, J.; Zeng, X. C. Polymorphism and Polyamorphism in Bilayer Water Confined to Slit Nanopore under High Pressure. Proceedings of the National Academy of Sciences of the United States of America, 2012, 109, 21240-21245.

5.

Zhao, W. H.; Wang, L.; Bai, J.; Yuan, L. F.; Yang, J.; Zeng, X. C. Highly Confined Water: Two-Dimensional ice, Amorphous Ice, and Clathrate Hydrates. Accounts of Chemical Research, 2014, 47, 2505-2513.

6.

Algara-Siller, G.; Lehtinen, O.; Wang, F. C.; Nair, R. R.; Kaiser, U.; Wu, H. A.; Geim, A. K.; Grigorieva, I. V. Square Ice in Graphene Nanocapillaries. Nature, 2015, 519, 443-445.

7.

Zhu, Y. B.; Wang, F. C.; Bai, J.; Zeng, X. C.; Wu, H. A. Compression Limit of Two-Dimensional Water Constrained in Graphene Nanocapillaries. ACS Nano, 2015, 9, 12197-12204.

8.

Bai, J.; Wang, J.; Zeng, X. C. Multiwalled Ice Helixes and Ice Nanotubes. Proceedings of the National Academy of Sciences of the United States of America, 2006, 103, 19664-19667.

9.

Takaiwa, D.; Hatano, I.; Koga, K.; Tanaka, H. Phase Diagram of Water in Carbon Nanotubes. Proceedings of the National Academy of Sciences of the United States of America, 2008, 105, 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

39-43. 10.

Koga, K.; Zeng, X. C.; Tanaka, H. Freezing of Confined Water: A Bilayer Ice Phase in Hydrophobic Nanopores. Phys. Rev. Lett. 1997, 79, 5262-5265.

11.

Zangi, R.; Mark, A. E. Monolayer Ice. Phys. Rev. Lett. 2003, 91, 025502/1-025502/4.

12.

Bai, J.; Angell, C. A.; Zeng, X. C. Guest-Free Monolayer Clathrate and Its Coexistence with Two-Dimensional High-Density Ice. Proceedings of the National Academy of Sciences of the United States of America, 2010, 107, 5718-5722.

13.

Mashl, R. J.; Joseph, S.; Aluru, N. R.; Jakobsson, E. Anomalously Immobilized Water: A New Water Phase Induced by Confinement in Nanotubes. Nano Lett. 2003, 3, 589-592.

14.

Koga, K.; Gao, G. T.; Tanaka, H.; Zeng, X. C. Formation of Ordered Ice Nanotubes inside Carbon Nanotubes. Nature. 2001, 412, 802-805.

15.

Koga, K.; Tanaka, H.; Zeng, X. C. First-Order Transition in Confined Water between High-Density Liquid and Low-Density Amorphous Phases. Nature 2000, 408, 564-567.

16.

Zangi, R.; Mark, A. E. Bilayer Ice and Alternate Liquid Phases of Confined Water. J. Chem. Phys. 2003, 119, 1694-1700.

17.

Han, S.; Choi, M. Y.; Kumar, P.; Stanley, H. E. Phase Transition in Confined Water Nanofilms. Nat. Phys. 2010, 6, 685-689.

18.

Giovambattista, N.; Rossky, P. J.; Debenedetti, P. G. Phase Transitions Induced by Nanoconfinement in Liquid Water. Phys Rev Lett, 2009, 102, 050603.

19.

Kastelowitz, N.; Johnston, J. C.; Molinero, V. The Anomalously High Melting Temperature of Bilayer Ice. The Journal of chemical physics, 2010, 132, 124511.

20.

Kumar, P.; Buldyrev, S. V.; Starr, F. W.; Giovambattista, N.; Stanley, H. E. Thermdynamics, Structure, and Dynamics of Water Confined between Hydrophobic Plates. Physical Review. E. 2005, 72, 051503.

21.

Jia, M.; Zhao, W. H.; Yuan, L. F. New Hexagonal-Rhombic Trilayer Ice Structure Confined between Hydrophobic Plates. Chinese Journal of Chemical Physics, 2014, 27, 15-19.

22.

Kumar, P.; Starr, F. W.; Buldyrev, S. V.; Stanley, H. E. Effect of Water-Wall Interaction Potential on the Properties of Nanoconfined Water. Physical Review. E. 2007, 75, 011202.

23.

Giovambattista, N.; Rossky, P. J.; Debenedetti, P. G. Effect of Pressure on the Phase Behavior and Structure of Water Confined between Nanoscale Hydrophobic and Hydrophilic Plates. Physical Review. E. 2006, 73, 041604.

24.

Giovambattista, N.; Debenedetti, P. G.; Rossky, P. J. Effect of Surface Polarity on Water Contact Angle and Interfacial Hydration Structure. The Journal of Physical Chemistry B. 2007, 111, 9581-9587.

25.

Giovambattista, N.; Debenedetti, P. G.; Rossky, P. J. Hydration behavior under confinement by nanoscale surfaces with patterned hydrophobicity and hydrophilicity. The Journal of Physical Chemistry C. 2007, 111, 1323-1332.

26.

Zangi, R.; Mark, A. E. Electrofreezing of Confined Water. The Journal of Chemical Physics, 2004, 120, 7123-7130.

27.

Qiu, H.; Zeng, X. C.; Guo, W. Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons. ACS Nano 2015, 9, 9877-9884.

28.

London, F. The General Theory of Molecular Force. Transactions of the Faraday Society. 1937, 33, 8b-26.

29.

Chen, j.; Schusteritsch, G.; Pickard, C. J.; Salzmann, C. G.; Michaelides, A. 2D ice from First 16


Page 16 of 18

Page 17 of 18

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Principles: Structures and Phase Transitions. arXiv: 1508.03743 [cond-mat.mtrl-sci]. 2015, 1508.03743. 30.

Corsetti, F.; Zubeltzu, J.; Artacho, E. Enhanced Residual Entropy in High-Density Nanoconfined Bilayer Ice. arXiv: 1506.04668 [cond-mat.soft]. 2015, 1506.04668

31.

Mario, S. F.; Neek-Amal, M.; Peeters, F. M. AA-Stacked Bilayer Square Ice between Graphene Layers. arXiv: 1509.08242 [cond-mat.mes-hall]. 2015, 1509.08242.

32.

Corsetti, F.; Matthews, P.; Artacho, E. Structural and Configurational Properties of Nanoconfined Monolayer Ice from First Principles. Scientific Reports, 2016, 6, 18651

33.

Jiao, S. P.; Xu, Z. P. Water under the Cover: Structures and Thermodynamics of Water Encapsulated by Graphene.

34.

Plimpton, S. J. Fast Parallel Algorithms for Short-Range Molecular Dynamics. Journal of Computational Physics. 1995, 117, 1-19.

35.

Abascal, J. L. F.; Vega, C. A General Purpose Model for the Condensed Phases of Water: TIP4P/2005. The Journal of Chemical Physics, 2005, 123, 234505.

36.

Bai, J.; Zeng, X. C.; Koga, K.; Tanaka, H. Formation of Quasi Two-Dimensional Bilayer Ice in Hydrophobic Slits: A Possible Candidate for Ice XIII? Molecular Simulation, 2003, 29, 619-626.

37.

Scheidler, P.; Kob, W.; Binder, K. Cooperative Motion and Growing Length Scales in Supercooled Confined Liquids. Europhysics Letters, 2002, 59, 701-707.

38.

Kaneko, T.; Bai, J.; Yasuoka, K.; Mitsutake, A.; Zeng, X. C. Liquid-Solid and Solid-Solid Phase Transition of Monolayer Water: High-Density Thombic Monolayer Ice. J. Chem. Phys. 2014, 140, 184507/1-184507/7

39.

Vega, C.; Sanz, E.; Abascal, J. L. The Melting Temperature of the Most Common Models of Water. J. Chem. Phys. 2005, 122, 114507.

40.

Werder, T.; Welther, J. H.; Jaffe, R. L.; Halicioglu, T.; Koumoutsakos, P. On the Water-Carbon Interaction for Use in Molecular Dynamics Simulations of Graphite and Carbon Nanotubes. J. Phys. Chem. B 2003, 107, 1345-1352

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Formation of Trilayer Ices in Graphene Nanocapillaries under High

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