Marios-Petros Kitsaras

Research Interests, Projects & Highlights

Highly Accurate Coupled-Cluster Methods

My research interest include developements and applications of highly accurate coupled-cluster methodologies, with particular emphasis on electronic properties and diagnostic tools for assessing wavefunction quality and electronic-structure character.

A notable example is my work on the calculation of spin contamination in approximate wavefunction based on an unrestricted reference, highlighted in the article “Spin contamination in MP2 and CC2, a surprising issue” .

Finite-Magnetic-Field Coupled-Cluster Theory

Finite magnetic-field coupled-cluster calculations
Image from: https://www.universetoday.com/152758/aging-white-dwarfs-become-even-more-magnetic/

I have developed and applied coupled-cluster approaches in the presence of strong magnetic fields, enabling the accurate interpretation of spectra originating from magnetic White-Dwarf stars. The finite-magnetic-field formulation employed in this line of work requires the use of complex-valued algebra, which substantially increases the computational cost. A central aspect of my research therefore focuses on the development of coupled-cluster approximations and their efficient implementation as to retain high accuracy while remaining computationally tractable.

Key contributions in this direction include the generalisation of existing models that account for perturbative triples corrections in the finite-magnetic-field framework, as demonstrated in “The approximate coupled-cluster methods CC2 and CC3 in a finite magnetic field” and “Equation-of-motion coupled-cluster variants in combination with perturbative triples corrections in strong magnetic fields” .

Building on these methodological developments, my work has enabled the assignment of spectroscopic signatures arising from metal atoms in a strongly magnetic White Dwarf for the first time, as reported in “A DZ white dwarf with a 30 MG magnetic field” .

Green’s Functions and Coupled-Cluster Connections

GW and BSE connection diagram

More recently, I have expanded my expertise to Green’s function approaches. These methods offer a powerful combination of efficiency and accuracy for the study of charged systems through the GW approximation and of electronically excited states through the Bethe–Salpeter equation (BSE). Importantly, they avoid the use of empirical parameters while achieving an accuracy comparable to coupled-cluster methods such as CCSD.

My background in both Green’s function methodologies and coupled-cluster theory allows me to exploit their intrinsic connections and to use this synergy as a platform for further methodological developments. A prominent example is my recent work on the implementation of analytic nuclear gradients at the G0W0 level of theory, as presented in “Analytic G0W0 gradients based on a double-similarity transformation equation-of-motion coupled-cluster treatment” .

I plan to further extend this line of research toward the combination of GW and BSE methods with molecular dynamics simulations, enabling the investigation of dynamical and finite-temperature effects in complex electronic systems.

Collaborators

Quantum Chemical Software

QCUMBRE logo QCUMBRE (maintainer) CFOUR logo CFOUR (contributor) COrbit19 logo COrbit19 (creator)

Curriculum Vitae

Education

Advanced Training and Schools

Professional and Academic Experience

Presentations and Invited Talks

Teaching Experience

Download CV (PDF)