Track internet usage in Linux

Recently, Nature published a paper titled "Superconductivity at 250 K in lanthanum hydride under high pressures" authored by Drozdov et al 2019 [Nature 569, 528–531 (2019)]

Special characters and symbols from MS Word

We might have come across some situation where we need some specific symbol and we don't now where it is in the symbol section that is provided by the Microsoft Office.

Here, is a way to get your special chearacter.

chi - this is a Greek letter and can be obtained using
Alt + 967 (press Alt key + 967)

insert - equation -
insert - object - get the best symbol.

List of Questions in DFT and answers (for some Qs)

The questions span a wide topics in Physics or sometimes other subjects also. Whenever possible, I try to answer in a separate post and give links to related materials to these question. To see the answer page, click the link ANSWER given at the end of the question.

A multi-electron wave function should obey Anti-symmetric priciple, i.e. the sign of the wave function should change sign if two electrons are interchanged (or swapped). Does Kohn-Sham orbitals obey this principle? Is there any description related to this? ANSWER

Peer-review: What it is like?

How is peer-review like?

Most of the time peer-review improves the manuscript. Here is an illustration (credit:redpenblackpen.jasonya.com) of how peer-review improves your manuscript. Originally, you submit a decent paper and if the manuscript is reviewed properly, surely it will transform your decent manuscript to a luxury car.

While peer-review some times gives so much pain for the authors, peer-review methodology works well.
"Yes. Exceptions too. There are so many research works which at the end got Nobel prize where initially rejected by peer-reviewers (as well as editors). A most recent example would be the first report on the atomically thick, 2D material cleaved from graphite known as Graphene. Firstly, the authors submitted the paper to Nature and it was rejected. Then, the authors made a minor revision in the paper and submitted to Science and it was published. Within 5 years after the publication of this paper, Nobel prize was awarded." This kind of rejections will be covered in another post.

But, here we are going to see so many examples where peer-review system is not that bad.

Challenge and Fun: Free your mind!

Have fun and challenge your mind from these links.

Take a stress test
Scott's amazing card trick
Optical Illusions
Jokes
Illusion Contest
Optical Illusions

Fortran Workflow

Fortran Specification Statements

by Michael Metcalf / CERN CN-AS
(taken from https://w3.pppl.gov/~hammett/comp/f90tut/f90.tut7.html
For a complete list of Fortran tutorial link and other useful links, look at
https://w3.pppl.gov/~hammett/

Implicit typing

The imlicit typing rules of FORTRAN 77 still hold. However, it is good practice to explicitly type all variables, and this can be forced by inserting the statement

        IMPLICIT NONE

at the beginning of each prorgam unit.

PARAMETER attribute

A named constant can be specified directly by adding the PARAMETER attribute and the constant values to a type statement:

     REAL, DIMENSION(3), PARAMETER :: field = (/ 0., 1., 2. /)
     TYPE(triplet), PARAMETER :: t =                           &
                                triplet( 0., (/ 0., 0., 0. /) )

DATA statement

The DATA statement can be used also for arrays and variables of derived type. It is also the only way to initialise just parts of such objects, as well as to initialise to binary, octal or hexadecimal values:

       TYPE(triplet) :: t1, t2
       DATA t1/triplet( 0., (/ 0., 1., 2. /) )/, t2%u/0./
       DATA array(1:64) / 64*0/
       DATA i, j, k/ B'01010101', O'77', Z'ff'/

Characters

There are many variations on the way character arrays may be specified. The shortest and longest are

CHARACTER name(4, 5)*20
CHARACTER (KIND = kanji, LEN = 20), DIMENSION (4, 5) :: name

Initialization expressions

The values used in DATA and PARAMETER statements, or with these attributes, are constant expressions that may include references to: array and structure constructors, elemental intrinsic functions with integer or character arguments and results, and the six transformational functions REPEAT, SELECTED_INT_KIND, TRIM, SELECTED_REAL_KIND, RESHAPE and TRANSFER:

     INTEGER, PARAMETER :: long = SELECTED_REAL_KIND(12),   &
                       array(3) = (/ 1, 2, 3 /)

Specification expressions

It is possible to specify details of variables using any non-constant, scalar, integer expression that may also include inquiry function references:

     SUBROUTINE s(b, m, c)
        USE mod                                 ! contains a
        REAL, DIMENSION(:, :)             :: b
        REAL, DIMENSION(UBOUND(b, 1) + 5) :: x
        INTEGER                              m
        CHARACTER(LEN=*)                     c
        CHARACTER(LEN= m + LEN(c))           cc
        REAL (SELECTED_REAL_KIND(2*PRECISION(a))) z

PUBLIC and PRIVATE

These attributes are used in specifications in modules to limit the scope of entities. The attribute form is

     REAL, PUBLIC     :: x, y, z           ! default
     INTEGER, PRIVATE :: u, v, w

and the statement form is

     PUBLIC  :: x, y, z, OPERATOR(.add.)
     PRIVATE :: u, v, w, ASSIGNMENT(=), OPERATOR(*)

The statement form has to be used to limit access to operators, and can also be used to change the overall default:

     PRIVATE                        ! sets default for module
     PUBLIC  :: only_this

For derived types there are three possibilities: the type and its components are all PUBLIC, the type is PUBLIC and its components PRIVATE (the type only is visible and one can change its details easily), or all of it is PRIVATE (for internal use in the module only):

     MODULE mine
        PRIVATE
        TYPE, PUBLIC :: list
           REAL x, y
           TYPE(list), POINTER :: next
        END TYPE list
        TYPE(list) :: tree
        :
     END MODULE mine

USE statement

To gain access to entities in a module, we use the USE statement. It has options to resolve name clashes if an imported name is the same as a local one:

     USE mine, local_list => list

or to restrict the used entities to a specified set:

     USE mine, ONLY : list

Compiling C, C++ and Fortran code using gnu/intel compilers

In general, compiling is done in three steps.

./configure --prefix=/home/userName/DirName

make or make all

Sometimes, the compiling error in a large code will be huge and may not be displayed in a single screen. It may be better to save the compiling error in a text file. This can be done using

make &> file.txt

make all &> file.txt

Research Flow

Pages