Université de Lyon (CNRS/ENS Lyon/UCB Lyon1), Centre de RMN à très hauts champs, 5 rue de la Doua, 69100 Villeurbanne, France.
J Chem Phys. 2010 Dec 14;133(22):224501. doi: 10.1063/1.3505455.
The design of simulations of free evolution in dipolar-coupled nuclear-spin systems using low-order correlations in Liouville space (LCL) is discussed, and a computational scheme relying on the Suzuki-Trotter algorithm and involving minimal memory requirements is described. The unusual nature of the approximation introduced by Liouville-space reduction in a spinning solid is highlighted by considering the accuracy of LCL simulations at different spinning frequencies, the quasiequilibria achieved by spin systems in LCL simulations, and the growth of high-order coherences in the exact dynamics. In particular, it is shown that accurate LCL simulations of proton spin diffusion occur in a regime where the reduced space excludes the coherences that make the dominant contribution to ∥σ∥(2), the norm-squared of the density matrix.
讨论了使用李算符空间（LCL）中的低阶关联来模拟偶极耦合核自旋系统中自由演化的设计，并描述了一种依赖于铃木-特罗特算法且内存需求最小的计算方案。通过考虑在旋转固体中李算符空间降阶所引入的近似的精度、LCL 模拟中自旋系统达到的准平衡状态以及在精确动力学中高阶相干的增长，突出了这种近似的不寻常性质。特别是，研究表明，在还原空间排除了对密度矩阵的二阶范数∥σ∥(2)有主要贡献的相干的情况下，准确的 LCL 质子自旋扩散模拟是可能的。
