start-ver=1.4 cd-journal=joma no-vol=115 cd-vols= no-issue=19 article-no= start-page=197801 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2015 dt-pub=20151106 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Chiral Ordering in Supercooled Liquid Water and Amorphous Ice en-subtitle= kn-subtitle= en-abstract= kn-abstract=The emergence of homochiral domains in supercooled liquid water is presented using molecular dynamics simulations. An individual water molecule possesses neither a chiral center nor a twisted conformation that can cause spontaneous chiral resolution. However, an aggregation of water molecules will naturally give rise to a collective chirality. Such homochiral domains possess obvious topological and geometrical orders and are energetically more stable than the average. However, homochiral domains cannot grow into macroscopic homogeneous structures due to geometrical frustrations arising from their icosahedral local order. Homochiral domains are the major constituent of supercooled liquid water and the origin of heterogeneity in that substance, and are expected to be enhanced in low-density amorphous ice at lower temperatures. en-copyright= kn-copyright= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University affil-num=3 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University END start-ver=1.4 cd-journal=joma no-vol=150 cd-vols= no-issue=21 article-no= start-page=214504 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190605 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A Bayesian approach for identification of ice Ih, ice Ic, high density, and low density liquid water with a torsional order parameter en-subtitle= kn-subtitle= en-abstract= kn-abstract= An order parameter is proposed to classify the local structures of liquid and solid water. The order parameter, which is calculated from the O–O–O–O dihedral angles, can distinguish ice Ih, ice Ic, high density, and low density liquid water. Three coloring schemes are proposed to visualize each of the coexisting phases in a system using the order parameter on the basis of Bayesian decision theory. The schemes are applied to a molecular dynamics trajectory in which ice nucleation occurs following spontaneous liquid-liquid separation in the deeply supercooled region as a demonstration. en-copyright= kn-copyright= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=151 cd-vols= no-issue=6 article-no= start-page=064702 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190808 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Formation of Hot Ice Caused by Carbon Nanobrushes en-subtitle= kn-subtitle= en-abstract= kn-abstract= Confinement in nanoscaled porous materials changes properties of water significantly. We perform molecular dynamics simulations of water in a model of a nanobrush made of carbon nanotubes. Water crystallizes into a novel structure called dtc in the nanobrush when (6,6) nanotubes are located in a triangular arrangement, and there is a space that can accommodate two layers of water molecules between the tubes. The mechanism of the solidification is analogous to formation of gas hydrates: hydrophobic molecules promote crystallization when their arrangement matches ordered structures of water. This is supported by a statistical mechanical calculation, which bears resemblance to the theory on the clathrate hydrate stability. en-copyright= kn-copyright= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamasakiMasaru en-aut-sei=Yamasaki en-aut-mei=Masaru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=150 cd-vols= no-issue=21 article-no= start-page=214506 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190606 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Liquid-liquid separation of aqueous solutions: A molecular dynamics study en-subtitle= kn-subtitle= en-abstract= kn-abstract= In the liquid-liquid phase transition scenario, supercooled water separates into the high density liquid (HDL) and low density liquid (LDL) phases at temperatures lower than the second critical point. We investigate the effects of hydrophilic and hydrophobic solutes on the liquid-liquid phase transition using molecular dynamics simulations. It is found that a supercooled aqueous NaCl solution separates into solute-rich HDL and solute-poor LDL parts at low pressures. By contrast, a supercooled aqueous Ne solution separates into solute-rich LDL and solute-poor HDL parts at high pressures. Both the solutes increase the high temperature limit of the liquid-liquid separation. The degree of separation is quantified using the local density of solute particles to determine the liquid-liquid coexistence region in the pressure-temperature phase diagram. The effects of NaCl and Ne on the phase diagram of supercooled water are explained in terms of preferential solvation of ions in HDL and that of small hydrophobic particles in LDL, respectively. en-copyright= kn-copyright= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=150 cd-vols= no-issue=4 article-no= start-page=041102 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190123 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Phase diagram of ice polymorphs under negative pressure considering the limits of mechanical stability en-subtitle= kn-subtitle= en-abstract= kn-abstract= Thermodynamic and mechanical stabilities of various ultralow-density ices are examined using computer simulations to construct the phase diagram of ice under negative pressure. Some ultralow-density ices, which were predicted to be thermodynamically metastable under negative pressures on the basis of the quasi-harmonic approximation, can exist only in a narrow pressure range at very low temperatures because they are mechanically fragile due to the large distortion in the hydrogen bonding network. By contrast, relatively dense ices such as ice Ih and ice XVI withstand large negative pressure. Consequently, various ices appear one after another in the phase diagram. The phase diagram of ice under negative pressure exhibits a different complexity from that of positive pressure because of the mechanical instability. en-copyright= kn-copyright= en-aut-name=MatsuiTakahiro en-aut-sei=Matsui en-aut-mei=Takahiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=16 cd-vols= no-issue=14 article-no= start-page=2460 end-page=2473 dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200424 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Lennard-Jones Parameters Determined to Reproduce the Solubility of NaCl and KCl in SPC/E, TIP3P, and TIP4P/2005 Water en-subtitle= kn-subtitle= en-abstract= kn-abstract=Most classical nonpolarizable ion potential models underestimate the solubility values of NaCl and KCl in water significantly. We determine Lennard-Jones parameters of Na+, K+, and Cl– that reproduce the solubility as well as the hydration free energy in dilute aqueous solutions for three water potential models, SPC/E, TIP3P, and TIP4P/2005. The ion–oxygen distance in the solution and the cation–anion distance in salt are also considered in the parametrization. In addition to the target properties, the hydration enthalpy, hydration entropy, self-diffusion coefficient, coordination number, lattice energy, enthalpy of solution, density, viscosity, and number of contact ion pairs are calculated for comparison with 17 frequently used or recently developed ion potential models. The overall performance of each ion model is represented by a global score using a scheme that was originally developed for comparison of water potential models. The global score is better for our models than for the other 17 models not only because of the quite good prediction for the solubility but also because of the relatively small deviation from the experimental value for many of the other properties. en-copyright= kn-copyright= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=1 cd-vols= no-issue=3 article-no= start-page=80 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20201217 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=On the Occurrence of Clathrate Hydrates in Extreme Conditions: Dissociation Pressures and Occupancies at Cryogenic Temperatures with Application to Planetary Systems en-subtitle= kn-subtitle= en-abstract= kn-abstract=We investigate the thermodynamic stability of clathrate hydrates at cryogenic temperatures from the 0 K limit to 200 K in a wide range of pressures, covering the thermodynamic conditions of interstellar space and the surface of the hydrosphere in satellites. Our evaluation of the phase behaviors is performed by setting up quantum partition functions with variable pressures on the basis of a rigorous statistical mechanics theory that requires only the intermolecular interactions as input. Noble gases, hydrocarbons, nitrogen, and oxygen are chosen as the guest species, which are key components of the volatiles in such satellites. We explore the hydrate/water two-phase boundary of those clathrate hydrates in water-rich conditions and the hydrate/guest two-phase boundary in guest-rich conditions, either of which occurs on the surface or subsurface of icy satellites. The obtained phase diagrams indicate that clathrate hydrates can be in equilibrium with either water or the guest species over a wide range far distant from the three-phase coexistence condition and that the stable pressure zone of each clathrate hydrate expands significantly on intense cooling. The implication of our findings for the stable form of water in Titan is that water on the surface exists only as clathrate hydrate with the atmosphere down to a shallow region of the crust, but clathrate hydrate in the remaining part of the crust can coexist with water ice. This is in sharp contrast to the surfaces of Europa and Ganymede, where the thin oxygen air coexists exclusively with pure ice. en-copyright= kn-copyright= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name=琢 kn-aut-sei= kn-aut-mei=琢 aut-affil-num=2 ORCID= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=154 cd-vols= no-issue=9 article-no= start-page=094502 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=20210301 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Formation of hot ice caused by carbon nanobrushes. II. Dependency on the radius of nanotubes en-subtitle= kn-subtitle= en-abstract= kn-abstract=Stable crystalline structures of confined water can be different from bulk ice. In Paper I [T. Yagasaki et al., J. Chem. Phys. 151, 064702 (2019)] of this study, it was shown, using molecular dynamics (MD) simulations, that a zeolite-like ice structure forms in nanobrushes consisting of (6,6) carbon nanotubes (CNTs) when the CNTs are located in a triangle arrangement. The melting temperature of the zeolite-like ice structure is much higher than the melting temperature of ice Ih when the distance between the surfaces of CNTs is ∼0.94 nm, which is the best spacing for the bilayer structure of water. In this paper, we perform MD simulations of nanobrushes of CNTs that are different from (6,6) CNTs in radius. Several new porous ice structures form spontaneously in the MD simulations. A stable porous ice forms when the radius of its cavities matches the radius of the CNTs well. All cylindrical porous ice structures found in this study can be decomposed into a small number of structural blocks. We provide a new protocol to classify cylindrical porous ice crystals on the basis of this decomposition. en-copyright= kn-copyright= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YagasakiTakuma en-aut-sei=Yagasaki en-aut-mei=Takuma kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=36 cd-vols= no-issue=18 article-no= start-page=10667 end-page=10674 dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20220628 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Structure Selectivity of Mixed Gas Hydrates and Group 14 Clathrates en-subtitle= kn-subtitle= en-abstract= kn-abstract=The structure selectivity of mixed gas hydrates and group 14 clathrates is examined on the basis of statistical mechanical theories and the empirical rule on the topological constraint of the Frank-Kasper phases. The most stable structure is revealed by the generalized phase diagram, where the chemical potential differences in the three canonical forms of clathrates are independent variables. The most stable structure incorporating individual guest species is evaluated by the locus of the chemical potential differences on this generalized phase diagram. We show that the method developed here is simple but powerful to estimate roughly phase behaviors of clathrate compounds in a wide range of thermodynamic conditions, which is demonstrated by two applications: the generalized phase diagram of group 14 element clathrates and the phase behavior of mixed gas hydrates. The present theory leads to proposals of phase change agents, of which the addition sensitively influences the structure selectivity, encompassing even minor structures. en-copyright= kn-copyright= en-aut-name=MatsumotoMasakazu en-aut-sei=Matsumoto en-aut-mei=Masakazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TanakaHideki en-aut-sei=Tanaka en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Toyota Physical and Chemical Research Institute kn-affil= END