Related Experiment Video
Updated: Aug 6, 2026
06:34
In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
Published on: September 2, 2016
Nodal Error behind Discrepancies between Coupled Cluster and Diffusion Monte Carlo
S Lambie1, P López Ríos1, D Kats1
1Max Planck Institute for Solid State Research, Heisenbergstraße 1, Stuttgart 70569, Germany.
Journal of Chemical Theory and Computation
|July 20, 2026
Summary
Computational quantum chemistry methods struggle with noncovalent interactions. Coupled cluster (CC) theory is confirmed as the benchmark, with diffusion Monte Carlo (DMC) errors primarily due to the fixed-node approximation.
Area of Science:
- Computational quantum chemistry
- Electronic structure theory
- Chemical physics
Background:
- Noncovalent interactions are crucial in chemistry and biology but challenging computationally.
- Coupled cluster (CC) theory and diffusion Monte Carlo (DMC) are advanced methods for studying these interactions.
- Discrepancies between CC and DMC results for interaction energies of noncovalently bound dimers have been noted.
Purpose of the Study:
- To systematically investigate the sources of error in CC and DMC calculations of noncovalent interactions.
- To determine the primary cause of discrepancies between CC and DMC methods.
- To establish a reliable benchmark method for studying noncovalent interactions.
Main Methods:
- Rigorous examination of approximations in CC and DMC methods.
- Utilizing acetic acid dimer and water-peptide systems for testing.
- Employing stringently optimized backflow wave functions in DMC calculations.
Main Results:
- Significant discrepancies between CC and DMC methods are primarily attributed to the fixed-node error in DMC.
- Approximations in coupled cluster calculations do not substantially affect the results.
- The fixed-node error in Slater-Jastrow DMC is identified as the dominant error source.
Conclusions:
- Coupled cluster (CC) theory should be considered the benchmark for calculating noncovalent interactions in systems like hydrogen-bonded dimers.
- Diffusion Monte Carlo (DMC) results are significantly impacted by the fixed-node approximation.
- This study provides insights for developing improved fixed-node approximations in DMC for future research.
More Related Videos
12:15Image Processing Protocol for the Analysis of the Diffusion and Cluster Size of Membrane Receptors by Fluorescence Microscopy
Published on: April 9, 2019
08:0915N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale
Published on: April 19, 2021
Related Concept Videos
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:17Differential Form of Maxwell's Equations
James Clerk Maxwell (1831–1879) was one of the significant contributors to physics in the nineteenth century. He is probably best known for having combined existing knowledge of the laws of electricity and the laws of magnetism with his insights to form a complete overarching electromagnetic theory, represented by Maxwell's equations. The four basic laws of electricity and magnetism were discovered experimentally through the work of physicists such as Oersted, Coulomb, Gauss, and Faraday.
01:20Maxwell-Boltzmann Distribution: Problem Solving
Individual molecules in a gas move in random directions, but a gas containing numerous molecules has a predictable distribution of molecular speeds, which is known as the Maxwell-Boltzmann distribution, f(v).
This distribution function f(v) is defined by saying that the expected number N (v1,v2) of particles with speeds between v1 and v2 is given by
This distribution function f(v) is defined by saying that the expected number N (v1,v2) of particles with speeds between v1 and v2 is given by
01:14NMR Spectrometers: Resolution and Error Correction
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
01:10Nodal Analysis
Nodal analysis is a fundamental method in electrical engineering used to simplify the process of circuit analysis. This method revolves around the concept of using node voltages as the primary variables for circuit analysis. The objective is to determine the voltage at each node in a circuit, which can then be used to find other quantities of interest, such as currents through specific components.
Consider, for instance, a simple circuit composed of three nodes and three resistors, as shown in...
Consider, for instance, a simple circuit composed of three nodes and three resistors, as shown in...
01:10Propagation of Uncertainty from Systematic Error
The atomic mass of an element varies due to the relative ratio of its isotopes. A sample's relative proportion of oxygen isotopes influences its average atomic mass. For instance, if we were to measure the atomic mass of oxygen from a sample, the mass would be a weighted average of the isotopic masses of oxygen in that sample. Since a single sample is not likely to perfectly reflect the true atomic mass of oxygen for all the molecules of oxygen on Earth, the mass we obtain from this particular...