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Administrator<br />

Connection Table . . . . . . . . . . . . . . . . . . . . . . . 118<br />

Gaussian Input . . . . . . . . . . . . . . . . . . . . . . . . . 118<br />

Gaussian Checkpoint . . . . . . . . . . . . . . . . . . . . 118<br />

Gaussian Cube . . . . . . . . . . . . . . . . . . . . . . . . . . 118<br />

Internal Coordinates . . . . . . . . . . . . . . . . . . . . 119<br />

MacroModel Files . . . . . . . . . . . . . . . . . . . . . . . 119<br />

Molecular Design Limited MolFile (.MOL) 120<br />

MSI ChemNote . . . . . . . . . . . . . . . . . . . . . . . . 120<br />

MOPAC Files . . . . . . . . . . . . . . . . . . . . . . . . . . 120<br />

MOPAC Graph Files . . . . . . . . . . . . . . . . . . . . 122<br />

Protein Data Bank Files . . . . . . . . . . . . . . . . . 122<br />

ROSDAL Files (RDL) . . . . . . . . . . . . . . . . . . 122<br />

Standard Molecular Data (SMD) . . . . . . . . 122<br />

SYBYL Files . . . . . . . . . . . . . . . . . . . . . . . . . . . 122<br />

Job Description File Formats . . . . . . . . . . . . . . . . 122<br />

JDF Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122<br />

JDT Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122<br />

Exporting With the Clipboard . . . . . . . . . . . . . . . 123<br />

Transferring to ChemDraw. . . . . . . . . . . . . . . . . 123<br />

Transferring to Other Applications. . . . . . . . . . 123<br />

Chapter 8: <strong>Com</strong>putation Concepts<br />

<strong>Com</strong>putational Methods Overview . . . . . . . . . . . 125<br />

Uses of <strong>Com</strong>putational Methods. . . . . . . . . . . . 126<br />

Choosing the Best Method . . . . . . . . . . . . . . . . . 126<br />

Molecular Mechanics Methods Applications<br />

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127<br />

Quantum Mechanical Methods Applications<br />

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127<br />

Potential Energy Surfaces . . . . . . . . . . . . . . . . 128<br />

Potential Energy Surfaces (PES) . . . . . . . . . . 129<br />

Single Point Energy Calculations . . . . . . . . . 129<br />

Geometry Optimization . . . . . . . . . . . . . . . . . 130<br />

Molecular Mechanics Theory in Brief . . . . . . . . . 131<br />

The Force-Field. . . . . . . . . . . . . . . . . . . . . . . . . . . 132<br />

MM2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132<br />

Bond Stretching Energy . . . . . . . . . . . . . . . . . 133<br />

Angle Bending Energy . . . . . . . . . . . . . . . . . . . 133<br />

Torsion Energy . . . . . . . . . . . . . . . . . . . . . . . . . 134<br />

Non-Bonded Energy . . . . . . . . . . . . . . . . . . . . 135<br />

van der Waals Energy . . . . . . . . . . . . . . . . . . . 135<br />

Cutoff Parameters for van der Waals<br />

Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135<br />

Electrostatic Energy . . . . . . . . . . . . . . . . . . . . . 136<br />

charge/charge contribution . . . . . . . . . . . . . . 136<br />

dipole/dipole contribution . . . . . . . . . . . . . . 136<br />

dipole/charge contribution . . . . . . . . . . . . . . 136<br />

Cutoff Parameters for Electrostatic<br />

Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . 136<br />

OOP Bending . . . . . . . . . . . . . . . . . . . . . . . . . . 137<br />

Pi Bonds and Atoms with Pi Bonds . . . . . . 137<br />

Stretch-Bend Cross Terms . . . . . . . . . . . . . . . 138<br />

User-Imposed Constraints . . . . . . . . . . . . . . . 138<br />

Molecular Dynamics Simulation . . . . . . . . . . . . 138<br />

Molecular Dynamics Formulas . . . . . . . . . . . 139<br />

Quantum Mechanics Theory in Brief . . . . . . . . . 139<br />

Approximations to the Hamiltonian . . . . . . 140<br />

Restrictions on the Wave Function . . . . . . . 141<br />

Spin functions . . . . . . . . . . . . . . . . . . . . . . . . . . 141<br />

LCAO and Basis Sets . . . . . . . . . . . . . . . . . . . 141<br />

The Roothaan-Hall Matrix Equation . . . . . . 142<br />

Ab Initio vs. Semiempirical . . . . . . . . . . . . . . 142<br />

The Semi-empirical Methods. . . . . . . . . . . . . . . 142<br />

Extended Hückel Method . . . . . . . . . . . . . . . 142<br />

Methods Available in CS MOPAC . . . . . . . . . . 143<br />

RHF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143<br />

UHF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143<br />

Configuration Interaction . . . . . . . . . . . . . . . 143<br />

Approximate Hamiltonians in MOPAC . . . . . . . 144<br />

Choosing a Hamiltonian. . . . . . . . . . . . . . . . . . . 144<br />

MINDO/3 Applicability and Limitations . 144<br />

MNDO Applicability and Limitations . . . . 145<br />

AM1 Applicability and Limitations . . . . . . . 145<br />

PM3 Applicability and Limitations . . . . . . . 146<br />

MNDO-d Applicability and Limitations . . 146<br />

Chapter 9: MM2 and MM3 <strong>Com</strong>putations<br />

Minimize Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . 147<br />

Running a Minimization . . . . . . . . . . . . . . . . . . . 149<br />

Queuing Minimizations . . . . . . . . . . . . . . . . . . . 150<br />

Minimizing Ethane . . . . . . . . . . . . . . . . . . . . . . . 150<br />

<strong>Com</strong>paring Two Stable Conformations of<br />

Cyclohexane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152<br />

Locating the Global Minimum . . . . . . . . . . . 153<br />

Molecular Dynamics . . . . . . . . . . . . . . . . . . . . . . . . 154<br />

Performing a Molecular Dynamics<br />

<strong>Com</strong>putation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154<br />

<strong>CambridgeSoft</strong>

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