Binding and excitations in Si${}_x$H${}_y$ molecular systems using quantum Monte Carlo

Abstract

We present high-accuracy correlated calculations of small Si${}_x$H${}_y$ molecular systems both in the ground and excited states. We employ quantum Monte Carlo (QMC) together with a variety of many-body wave function approaches based on basis set expansions. The calculations are carried out in a valence-only framework using recently derived correlation consistent effective core potentials. Our primary goal is to understand the fixed-node diffusion QMC errors in both the ground and excited states with single-reference trial wave functions. Using a combination of methods, we demonstrate the very high accuracy of the QMC atomization energies being within $\approx$ 0.07 eV or better when compared with essentially exact results. By employing proper choices for trial wave functions, we have found that the fixed-node QMC biases for total energies are remarkably uniform ranging between $1-3.5$ % with absolute values at most $\approx$ 0.2 eV across the systems and several types of excitations such as singlets and triplets as well as low-lying and Rydberg-like states. Our results further corroborate that Si systems, and presumably also related main group IV and V elements of the periodic table (Ge, Sn, etc), exhibit some of the lowest fixed-node biases found in valence-only electronic structure QMC calculations.

arXiv comment10 pages, 1 figure

References in corpus (22)

• QMCPACK : An open source ab initio Quantum Monte Carlo package for the electronic structure of atoms, molecules, and solids
• Beyond the locality approximation in the standard diffusion Monte Carlo method
• High Accuracy Many-Body Calculational Approaches for Excitations in Molecules
• A Data Ecosystem to Support Machine Learning in Materials Science
• Quantum Package 2.0: An Open-Source Determinant-Driven Suite of Programs
• QMCPACK: Advances in the development, efficiency, and application of auxiliary field and real-space variational and diffusion Quantum Monte Carlo
• Size-consistent variational approaches to non-local pseudopotentials: standard and lattice regularized diffusion Monte Carlo methods revisited
• A New Generation of Effective Core Potentials for Correlated Calculations
• New generation of effective core potentials from correlated calculations: 3d transition metal series
• Optimized Jastrow-Slater wave functions for ground and excited states: Application to the lowest states of ethene
• New generation of effective core potentials from correlated calculations: 2nd row elements
• Discovering correlated fermions using quantum Monte Carlo
• Toward an improved control of the fixed-node error in quantum Monte Carlo: The case of the water molecule
• Structure of fermion nodes and nodal cells
• Almost exact energies for the Gaussian-2 set with the semistochastic heat-bath configuration interaction method
• Excited states with selected CI-QMC: chemically accurate excitation energies and geometries
• Perturbatively selected configuration-interaction wave functions for efficient geometry optimization in quantum Monte Carlo
• Phaseless Auxiliary-Field Quantum Monte Carlo on Graphical Processing Units
• A new generation of effective core potentials from correlated calculations: 4s and 4p main group elements and first row additions
• Using CIPSI nodes in diffusion Monte Carlo
• Fixed-node errors in quantum Monte Carlo: interplay of electron density and node nonlinearities
• Accurate atomic correlation and total energies for correlation consistent effective core potentials

Cited by in corpus (7)

• Systematic DFT+U and Quantum Monte Carlo benchmark of magnetic two-dimensional (2D) CrX${}_3$ (X = I, Br, Cl, F)
• Cohesion and excitations of diamond-structure silicon by quantum Monte Carlo: Benchmarks and control of systematic biases
• The intrinsic ferromagnetism of two-dimensional (2D) MnO${}_2$ revisited: A many-body Quantum Monte Carlo and DFT+U study
• The role of electron correlations in the electronic structure of putative Chern magnet TbMn${}_6$Sn${}_6$
• A pathway towards high throughput Quantum Monte Carlo simulations for alloys: A case study of two-dimensional (2D) $Ga{S}_{x}S{e}_{1-x}$
• Electronic structure of $\mathbf{\alpha }$-RuCl${}_3$ by fixed-node and fixed-phase diffusion Monte Carlo methods
• Weighted nodal domain averages of eigenstates for quantum Monte Carlo and beyond