Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry.
Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry.
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DOI：
10.1073/pnas.2018379118
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发表时间：
2021-02-09
影响因子：
11.1
通讯作者：
Nilsson A
中科院分区：
文献类型：
--
作者：
Pathak H;Späh A;Esmaeildoost N;Sellberg JA;Kim KH;Perakis F;Amann-Winkel K;Ladd-Parada M;Koliyadu J;Lane TJ;Yang C;Lemke HT;Oggenfuss AR;Johnson PJM;Deng Y;Zerdane S;Mankowsky R;Beaud P;Nilsson A
了解分子结构、动力学的重要性。液态水的性质在许多科学学科中都得到了承认。在这里，我们实验研究了大量的液态水的结构和热力学，因为它是通过蒸发过冷到10228 K。这项工作的独特之处在于使用超快量热法，使我们能够确定水在前所未有的低温下的比热容。在229 K时观察到的最大值约为218 J/mol/K，与液-液临界点模型一致，并支持在220 K时提出的脆-强转变，以解释估计的自扩散系数在235 K以下急剧下降。等压比热（Cp）对深度过冷的温度依赖性的知识可以提供关于水的异常性质的见解。如果Cp在特定温度下存在最大值，如等温压缩性，则将进一步验证可以解释热力学响应函数异常增加的液-液临界点模型。挑战在于相关的温度范围福尔斯落在冰结晶变得迅速的区域，这在以前排除了实验。在这里，我们已经利用了超快量热法的方法，通过确定从飞秒X射线脉冲加热后的温度跳跃与红外激光脉冲和脉冲之间的足够长的时间延迟，以允许在恒定的压力下测量。在真空中蒸发冷却直径为15 μm的液滴使我们能够达到228 K的温度，其中一小部分液滴保持不冻结。我们观察到Cp的急剧增加，从244 K时的88 J/mol/K增加到229 K时的约218 J/mol/K，其中观察到最大值。Cp最大值与等温压缩系数和相关长度的最大值处于相似的温度。从Cp测量中，我们估计了水的过剩熵和自扩散系数，这些性质在235 K以下迅速下降。
The importance of molecular understanding of the structure, dynamics. and properties of liquid water is recognized in many scientific disciplines. Here, we study experimentally the structure and thermodynamics of bulk liquid water as it is supercooled by evaporation down to ∼228 K. The unique aspect of this work is the use of ultrafast calorimetry that enables us to determine the specific-heat capacity of water to unprecedentedly low temperatures. The observed maximum of about 218 J/mol/K at 229 K is consistent with the liquid–liquid critical point model and supports a proposed fragile-to-strong transition at ∼220 K to explain the steep decrease in the estimated self-diffusion coefficient below 235 K. Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid–liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.
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影响因子：
16.6
作者：
Gallo, P.;Corradini, D.;Rovere, M.
通讯作者：
Rovere, M.
影响因子：
5.7
作者：
Holten, Vincent;Qiu, Chen;Caupin, Frederic
通讯作者：
Caupin, Frederic
影响因子：
4.4
作者：
Hestand, Nicholas J.;Skinner, J. L.
通讯作者：
Skinner, J. L.
DOI：
10.1021/acs.jpclett.5b01164
发表时间：
2015-07-16
期刊：
The journal of physical chemistry letters
影响因子：
--
作者：
Laksmono H;McQueen TA;Sellberg JA;Loh ND;Huang C;Schlesinger D;Sierra RG;Hampton CY;Nordlund D;Beye M;Martin AV;Barty A;Seibert MM;Messerschmidt M;Williams GJ;Boutet S;Amann-Winkel K;Loerting T;Pettersson LG;Bogan MJ;Nilsson A
通讯作者：
Nilsson A
影响因子：
8.6
作者：
Goy, Claudia;Potenza, Marco A. C.;Grisenti, Robert E.
通讯作者：
Grisenti, Robert E.