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Title: Ab initio molecular dynamics with noisy forces: Validating the quantum Monte Carlo approach with benchmark calculations of molecular vibrational properties

We present a systematic study of a recently developed ab initio simulation scheme based on molecular dynamics and quantum Monte Carlo. In this approach, a damped Langevin molecular dynamics is employed by using a statistical evaluation of the forces acting on each atom by means of quantum Monte Carlo. This allows the use of an highly correlated wave function parametrized by several variational parameters and describing quite accurately the Born-Oppenheimer energy surface, as long as these parameters are determined at the minimum energy condition. However, in a statistical method both the minimization method and the evaluation of the atomic forces are affected by the statistical noise. In this work, we study systematically the accuracy and reliability of this scheme by targeting the vibrational frequencies of simple molecules such as the water monomer, hydrogen sulfide, sulfur dioxide, ammonia, and phosphine. We show that all sources of systematic errors can be controlled and reliable frequencies can be obtained with a reasonable computational effort. This work provides convincing evidence that this molecular dynamics scheme can be safely applied also to realistic systems containing several atoms.
Authors:
;  [1] ;  [2]
  1. International School for Advanced Studies (SISSA), and CRS Democritos, CNR-INFM, Via Bonomea 265, I-34136 Trieste (Italy)
  2. Dipartimento di Fisica, Università di Roma “La Sapienza,” Piazzale Aldo Moro 2, I-00185 Rome (Italy)
Publication Date:
OSTI Identifier:
22415371
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 19; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 97 MATHEMATICAL METHODS AND COMPUTING; ACCURACY; AMMONIA; BORN-OPPENHEIMER APPROXIMATION; EVALUATION; HYDROGEN SULFIDES; MOLECULAR DYNAMICS METHOD; MOLECULES; MONTE CARLO METHOD; SIMULATION; SULFUR DIOXIDE; SURFACES