Related Experiment Video
Updated: Jun 2, 2026

Using Three-color Single-molecule FRET to Study the Correlation of Protein Interactions
Published on: January 30, 2018
Sensitivity analysis of state-specific multireference perturbation theory
1Laboratory of Theoretical Chemistry, Loránd Eötvös University, Budapest, Hungary. szabados@chem.elte.hu
Abstract:
State-specific multireference perturbation theory (SS-MRPT) developed by Mukherjee et al. [Int. J. Mol. Sci. 3, 733 (2002)] is examined focusing on the dependence of the perturbed energy on the initial model space coefficients. It has been observed earlier, that non-physical kinks may appear on the potential energy surface obtained by SS-MRPT while related coupled-cluster methods may face convergence difficulties. Though exclusion or damping of the division by small coefficients may alleviate the problem, it is demonstrated here that the effect does not originate in an ill-defined division. It is shown that non-negligible model space coefficients may also be linked with the problem. Sensitivity analysis is suggested as a tool for detecting the coefficient responsible. By monitoring the singular values of sensitivity matrices, orders of magnitude increase is found in the largest value, in the vicinity of the problematic geometry point on the potential energy surface. The drastic increase of coefficient sensitivities is found to be linked with a degeneracy of the target root of the effective Hamiltonian. The nature of the one-electron orbitals has a profound influence on the picture: a rotation among active orbitals may screen or worsen the effect.
Related Concept Videos
State Function, Exact and Inexact Differentials
Mechanistic Models: Compartment Models in Individual and Population Analysis
State Space Representation
Consider an RLC circuit, a...
Linear Approximation in Time Domain
For a simple pendulum with a mass evenly distributed along its length and the center of mass located at half the pendulum's length, the...
Propagation of Uncertainty from Systematic Error
Propagation of Uncertainty from Random Error
