Thermal Effects in Atomic and Molecular Polarizabilities with Path Integral Monte Carlo
Research output: Book/Report › Doctoral thesis › Collection of Articles
|Number of pages||120|
|Publication status||Published - 5 Apr 2019|
|Publication type||G5 Doctoral dissertation (article)|
|Name||Tampere University Dissertations|
The Thesis contains an introduction to polarizability in the framework of nonrelativistic Feynman path integrals and thermal density matrices. The electric ﬁeld interactions due to electric multipoles is associated with causal time-correlation functions and nonlinear response theory. The original scientiﬁc contribution manifests in various strategies to obtain the polarizabilities from PIMC simulations: we demonstrate ﬁnite-ﬁeld simulations, static ﬁeld-derivative estimators, and analytic continuation of imaginarytime correlation functions. The required analytic continuation of Matsubara frequencies is a common but ill-posed numerical challenge, which we approach with the Maximum Entropy method.
For data, we provide the most important polarizabilities and hyperpolarizabilities of several one- or two-electron systems: H, H2+, H2, H3+, HD+, He, He+, HeH+, Li+, Be2+, Ps, PsH, and Ps2. Our benchmark simulations within the Born–Oppenheimer approximation (BO) agree with the available literature and complement it in many cases. Beyond BO, we are able to demonstrate weak and strong thermal effects due to, e.g., rovibrational coupling. We also estimate the ﬁrst-order multipole spectra, dynamic polarizabilities and van der Waals coefﬁcients. The simulations show unprecedented accuracy in terms of exact many-body correlations and fully nonadiabatic coupling of the electronic and nuclear quantum effects.