Madarász Ádám, Laczkó Gergely
Research Centre for Natural Sciences, Magyar Tudósok Körútja 2, Budapest H-1117, Hungary.
Hevesy György PhD School of Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest H-1518, Hungary.
J Chem Theory Comput. 2024 Nov 12;20(21):9562-9570. doi: 10.1021/acs.jctc.4c00564. Epub 2024 Oct 15.
In path integral molecular dynamics (PIMD) simulations, atoms are represented by several replicas connected with harmonic springs, so additional vibrations appear beyond the physical vibrations because of the normal mode frequencies coming from the springs of the ring polymer. In harmonic approximation, the frequencies of these internal modes can be determined exactly from the physical frequencies. We show that this formal effect of the path integral simulations on the vibrations can be considered as a convolution if we use the square of the frequency as an independent variable. This convolution can be represented as a matrix multiplication. The potential of the formalism is demonstrated in two applications. We present an alternative method to determine the power spectrum of thermostats used in PIMD simulations. We also show that in simple anharmonic model systems, the physical frequencies can be obtained from ring polymer molecular dynamics simulations by deconvolution, even in cases where spurious resonances appear.
在路径积分分子动力学（PIMD）模拟中，原子由通过谐振子弹簧连接的多个副本表示，因此由于来自环形聚合物弹簧的正常模式频率，除了物理振动之外还会出现额外的振动。在简谐近似中，这些内部模式的频率可以根据物理频率精确确定。我们表明，如果我们将频率的平方作为自变量，路径积分模拟对振动的这种形式上的影响可以被视为一种卷积。这种卷积可以表示为矩阵乘法。该形式体系的潜力在两个应用中得到了证明。我们提出了一种确定PIMD模拟中使用的恒温器功率谱的替代方法。我们还表明，在简单的非简谐模型系统中，即使在出现虚假共振的情况下，也可以通过去卷积从环形聚合物分子动力学模拟中获得物理频率。
