Updating the Hessian

relax provides a variety of methods to generate an updated Hessian every cycle. This includes the well known methods such as BFGS, DFP, or MS update methods as well as some less common procedures:

--------------------------------------------------------------
OPTIONS FOR UPDATING THE HESSIAN
--------------------------------------------------------------
 option  | status | description
--------------------------------------------------------------
none     |    F   | NO UPDATE (STEEPEST DESCENT)
bfgs     |    F   | BROYDEN-FLETCHER-GOLDFARB-SHANNO UPDATE
dfp      |    F   | DAVIDON-FLETCHER-POWELL UPDATE
bfgs-dfp |    F   | COMBINED (BFGS+DFP) UPDATE
ms       |    F   | MURTAGH-SARGENT UPDATE
schlegel |    F   | SCHLEGEL UPDATE
diagup   |    F   | DIAGONAL UPDATE (AHLRICHS/EHRIG)
multidim |    F   | RANK > 2 BFGS-TYPE UPDATE
ahlrichs |    T   | MACRO : AHLRICHS UPDATE (DEFAULT)
--------------------------------------------------------------
USE <opt> FOR ENABLING OPTION <opt> AND THUS DISABLING
ALL OTHER OPTIONS.
<RETURN> OR * OR q(uit) WILL TERMINATE THIS MENU

We recommend to use the default method ahlrichs which provides excellent convergency in most cases.