Category Archives: physics

Manual for tdhf

tdhf - is a Dirac-Hartree-Fock program developed by Walter R. Johnson
Calculates energies and w.f. of valence electrons. Has Breit + QED corrections

tdhf input

read(5,1000) ident,jmax,jz,nat,nuc,ion,io, in, inf [format(a4,4i8)]
Example Fr 30 87 223 0 0 9 25 1

character*4 $ident = atomic element symbol {e.g., Fr}
$jmax = # of input fields with shell orbital description (see below)
$jz  = nuclear charge Z (atomic number for neutrals)
$nat = atomic mass number A ( atomic weight)
$nuc = (unused set to 0)
$ion = (unused set to 0)
$io = Desired relative precision = 10^(-io) - controls convergence criteria
$in = index of the 1-st valence shell in the cards with orbital description (below)
$inf = (0 or 1) 0=closed-shell only
if 1 do a solution for valence electron in the frozen core approximation

Cards with orbital description:
total number $jmax (above)
* ( n(i),kap(i),iof(i),wh(i), i = 1,jmax ) format(3i4,f12.4)
card format : n kappa iof guessed_energy_in_a.u.
* n(i): principal quantun number
* kap(i): angular quantum number kappa

if $guessed_energy >= 0.0 it is calculated internally from the hydrogenic formula
The guessed_energy for valence orbitals better be good, since the program gives some dumb answers if the hydrogenic default is used.
$iof governs some internal step, the mixing weight between previous and next iteration

the first $in cards describe core orbitals the rest $jz -$in are valence orbitals

if $inf was 1 the next input is
$xa xalpha  (some mixing parameter)

read(5,*) r0,hh,mm

These are grid parameters

read(5,*) iparm

$iparm = Type of nuclear parameters
if $iparm = 1 rnuc,cnuc,tnuc expected (all in fermis).

if $iparm != 1: cnuc,anuc,b2,b4

For example for Fr the relevant input is
1.00 ! iparm
.00000 6.83430 2.30000 !rnuc,cnuc,tnuc

We mostly use $iparm = 1. Nuclear parameters can be found here (NuclearPropsWRJ.pdf)
In this table tnuc=2.3 fm; rnuc=0.0000 and the relevant parameter is C(fm)

read(5,*) ex

$ex  affects amount of exchange in the Hartree model potential for initializing valence+frozen core potential.
Nominal value = 0

Related posts:

  1. Tweaking Mathematica output for order-of-magnitude estimates

Stepping stones or the value of theory

photo of stepping stones across a lake

"Way In The Lake" by Evgeni Dinev

When invited to present colloquia talks, I usually talk about atomic clocks and I am sometimes asked what a theorist is doing in this highly experimental field. I was thinking about this question for a while and then I was on a plane browsing through an in-flight catalog (you know the one that advertises stuff that you may want but really do not need) and I realized how to answer this question.

There was an ad for a beautiful wristwatch accompanied by a story on the fine craft  of clockmaking. The story was comparing making a wristwatch to building a skyscraper out of matchsticks. So I thought, by that account, experimentalists working on atomic clocks are performing miracles. And if these  experimentalists are walking on water, my role as a theorist is to show them where the stepping stones are.

Related posts:

  1. When would an unanticipated “new physics” event be apparent to an unsuspecting experimentalist?
  2. The world's time

Pauli's letter or the importance of technical details

This is one of my favorite illustrations of the importance of technical details. Below I am posting a figure from a paper by Peter Woit, where the Pauli's letter is displayed.

In 1958, Wolfgang Pauli sent letters to some fellow physicists, making fun of Werner Heisenberg's exaggerated claims to have developed a successful unified
theory. A copy of his letter to J. Robert Oppenheimer is shown here.

A letter of Pauli to Oppenheimer

The letter says: Comment on Heisenberg Radio advertisement.
This is to show the world that I can paint like Titian. [Empty frame with jagged sides]. Only technical details are missing.

Here is  a link to a similar letter to Gamov.

No related posts.