# Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems

## Abstract

In this chapter we focus on methodological and computational aspects that are key to accurately modeling the spectroscopic and thermodynamic properties of molecular systems containing actinides within the density functional theory (DFT) framework. Our focus is on properties that require either an accurate relativistic all-electron description or an accurate description of the dynamical behavior of actinide species in an environment at finite temperature, or both. The implementation of the methods and the calculations discussed in this chapter were done with the NWChem software suite (Valiev et al. 2010). In the first two sections we discuss two methods that account for relativistic effects, the ZORA and the X2C Hamiltonian. Section 1.2.1 discusses the implementation of the approximate relativistic ZORA Hamiltonian and its extension to magnetic properties. Section 1.3 focuses on the exact X2C Hamiltonian and the application of this methodology to obtain accurate molecular properties. In Section 1.4 we examine the role of a dynamical environment at finite temperature as well as the presence of other ions on the thermodynamics of hydrolysis and exchange reaction mechanisms. Finally, Section 1.5 discusses the modeling of XAS (EXAFS, XANES) properties in realistic environments accounting for both the dynamics of the system and (for XANES)more »

- Authors:

- Publication Date:

- Research Org.:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1179509

- Report Number(s):
- PNNL-SA-101465

44669; KC0302030

- DOE Contract Number:
- AC05-76RL01830

- Resource Type:
- Book

- Resource Relation:
- Related Information: Computational Methods in Lanthanide and Actinide Chemistry, 299-342

- Country of Publication:
- United States

- Language:
- English

- Subject:
- Lanthanide; actinide; chemistry; density functional theory; NWChem; calculations; Environmental Molecular Sciences Laboratory

### Citation Formats

```
Autschbach, Jochen, Govind, Niranjan, Atta Fynn, Raymond, Bylaska, Eric J., Weare, John H., and de Jong, Wibe A.
```*Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems*. United States: N. p., 2015.
Web. doi:10.1002/9781118688304.ch12.

```
Autschbach, Jochen, Govind, Niranjan, Atta Fynn, Raymond, Bylaska, Eric J., Weare, John H., & de Jong, Wibe A.
```*Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems*. United States. doi:10.1002/9781118688304.ch12.

```
Autschbach, Jochen, Govind, Niranjan, Atta Fynn, Raymond, Bylaska, Eric J., Weare, John H., and de Jong, Wibe A. Mon .
"Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems". United States.
doi:10.1002/9781118688304.ch12.
```

```
@article{osti_1179509,
```

title = {Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems},

author = {Autschbach, Jochen and Govind, Niranjan and Atta Fynn, Raymond and Bylaska, Eric J. and Weare, John H. and de Jong, Wibe A.},

abstractNote = {In this chapter we focus on methodological and computational aspects that are key to accurately modeling the spectroscopic and thermodynamic properties of molecular systems containing actinides within the density functional theory (DFT) framework. Our focus is on properties that require either an accurate relativistic all-electron description or an accurate description of the dynamical behavior of actinide species in an environment at finite temperature, or both. The implementation of the methods and the calculations discussed in this chapter were done with the NWChem software suite (Valiev et al. 2010). In the first two sections we discuss two methods that account for relativistic effects, the ZORA and the X2C Hamiltonian. Section 1.2.1 discusses the implementation of the approximate relativistic ZORA Hamiltonian and its extension to magnetic properties. Section 1.3 focuses on the exact X2C Hamiltonian and the application of this methodology to obtain accurate molecular properties. In Section 1.4 we examine the role of a dynamical environment at finite temperature as well as the presence of other ions on the thermodynamics of hydrolysis and exchange reaction mechanisms. Finally, Section 1.5 discusses the modeling of XAS (EXAFS, XANES) properties in realistic environments accounting for both the dynamics of the system and (for XANES) the relativistic effects.},

doi = {10.1002/9781118688304.ch12},

journal = {},

number = ,

volume = ,

place = {United States},

year = {Mon Mar 30 00:00:00 EDT 2015},

month = {Mon Mar 30 00:00:00 EDT 2015}

}