Bhowmick Somnath, Hernández Marta I, Campos-Martínez José, Suleimanov Yury V
Computation-based Science and Technology Research Center, The Cyprus Institute, 20 Konstantinou Kavafi Street, Nicosia 2121, Cyprus.
Phys Chem Chem Phys. 2021 Sep 14;23(34):18547-18557. doi: 10.1039/d1cp02121d. Epub 2021 Aug 13.
Microscopic-level understanding of the separation mechanism for two-dimensional (2D) membranes is an active area of research due to potential implications of this class of membranes for various technological processes. Helium (He) purification from the natural resources is of particular interest due to the shortfall in its production. In this work, we applied the ring polymer molecular dynamics (RPMD) method to graphdiyne (Gr2) and graphtriyne (Gr3) 2D membranes having variable pore sizes for the separation of He isotopes, and compare for the first time with rigorous quantum calculations. We found that the transmission rate through Gr3 is many orders of magnitude greater than Gr2. The selectivity of either isotope at low temperatures is a consequence of a delicate balance between the zero-point energy effect and tunneling of He and He. In particular, a remarkable tunneling effect is reported on the Gr2 membrane at 10 K, leading to a much larger permeation of the lighter species as compared to the heavier isotope. RPMD provides an efficient approach for studying the separation of He isotopes, taking into account quantum effects of light nuclei motions at low temperatures, which classical methods fail to capture.
由于二维（2D）膜在各种技术过程中的潜在应用，对其分离机制的微观层面理解是一个活跃的研究领域。由于氦（He）产量短缺，从自然资源中提纯氦尤为重要。在这项工作中，我们将环形聚合物分子动力学（RPMD）方法应用于具有可变孔径的石墨二炔（Gr2）和石墨三炔（Gr3）二维膜，用于分离氦同位素，并首次与严格的量子计算进行比较。我们发现，通过Gr3的传输速率比Gr2大许多个数量级。在低温下，任何一种同位素的选择性都是零点能量效应与He和He隧穿之间微妙平衡的结果。特别是，在10 K时，Gr2膜上报告了显著的隧穿效应，导致较轻物种比较重同位素的渗透量大得多。RPMD提供了一种研究氦同位素分离的有效方法，考虑到了低温下轻核运动的量子效应，而经典方法无法捕捉这些效应。
