From ad2eb00453016cbd6029b550b01a47f3d2dc0142 Mon Sep 17 00:00:00 2001
From: hu-jingnan <d202180127@hust.edu.cn>
Date: Fri, 10 May 2024 13:08:05 +0800
Subject: [PATCH] Add files via upload

---
 math_lib.f90 | 193 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 193 insertions(+)
 create mode 100644 math_lib.f90

diff --git a/math_lib.f90 b/math_lib.f90
new file mode 100644
index 00000000..63447e0f
--- /dev/null
+++ b/math_lib.f90
@@ -0,0 +1,193 @@
+!> Here we put a set of basic mathematic operations
+function det3(a)
+   !> calculate the determinant of a real valued rank-3 matrix
+   use para, only : dp
+   implicit none
+   real(dp) :: det3
+   real(dp), intent(in) :: a(3, 3)
+
+   det3= a(1,1)*(a(2,2)*a(3,3)-a(3,2)*a(2,3)) &
+         +a(2,1)*(a(3,2)*a(1,3)-a(1,2)*a(3,3)) &
+         +a(3,1)*(a(1,2)*a(2,3)-a(2,2)*a(1,3))
+
+   return
+end function det3
+
+!> Get the angle between two given vectors which are in cartesian coordinates
+!> return in degree
+function angle(R1, R2)
+   use para, only : dp, pi
+
+   implicit none
+   real(dp), intent(in) :: R1(3), R2(3)
+   real(dp) :: angle, adotb
+   real(dp), external :: norm
+ 
+   adotb=dot_product(R1, R2)
+   angle= acos(adotb/norm(R1)/norm(R2))*180d0/pi
+
+   return
+end function angle
+
+!> Get the length of a given 3-value vector
+function norm(R1)
+   use para, only : dp
+
+   implicit none
+   real(dp), intent(in) :: R1(3)
+   real(dp) :: norm1
+   real(dp) :: norm
+
+   norm1= R1(1)*R1(1)+ R1(2)*R1(2)+ R1(3)*R1(3)
+   norm= sqrt(norm1)
+
+   return
+end function norm
+
+!> shift the atom's position to the home unit cell
+!> shift pos_direct_pc to the home unit cell (-0.5, 0.5]
+subroutine in_home_cell_regularization(pos)
+   use para, only : dp, eps3, pi
+
+   implicit none
+
+   real(dp), intent(inout) :: pos(3)
+
+   integer :: i
+   real(dp) :: irrational_shift(3)
+   irrational_shift= (/ pi/1000d0, pi/1000d0, 0d0 /)
+   pos= pos+ irrational_shift
+
+   pos= pos-floor(pos)
+
+   do i=1, 3
+      if (abs(pos(i)-1)<0.03d0) pos(i)= 1d0
+      if (abs(pos(i)-0.5)<0.03d0) pos(i)= 0.5d0
+      if (pos(i)>0.5000000d0) pos(i)= pos(i)-1d0
+   enddo
+   pos= pos- irrational_shift
+
+   return
+end subroutine in_home_cell_regularization
+
+
+
+!> the shortest difference betwerrn two vectors with respect to the lattice vectors
+subroutine periodic_diff_1D(R2, R1, diff)
+   !> diff= mod(R2-R1, 1)
+   use para, only : dp
+
+   implicit none
+
+   real(dp), intent(in) :: R1, R2
+   real(dp), intent(out) :: diff
+
+   integer :: i
+
+   diff= R2-R1
+   diff= diff-floor(diff)
+
+   if (diff>0.5000000d0) diff= diff-1d0
+
+   return
+end subroutine periodic_diff_1D
+
+!> shift the atom's position to the home unit cell
+!> shift pos_direct_pc to the home unit cell [-0.5, 0.5)
+subroutine in_home_cell(R0)
+   use para, only : dp
+
+   implicit none
+
+   real(dp), intent(inout) :: R0(3)
+
+   integer :: i
+
+   R0= R0-int8(R0)
+
+   do i=1, 3
+      if (R0(i)>=0.5000000d0) R0(i)= R0(i)-1d0
+   enddo
+
+   R0= R0+ 0.5d0
+   R0= mod(R0, 1d0)
+
+   return
+end subroutine in_home_cell
+
+
+
+!> the shortest difference betwerrn two vectors with respect to the lattice vectors
+subroutine periodic_diff(R2, R1, diff)
+   !> diff= mod(R2-R1, 1)
+   use para, only : dp
+
+   implicit none
+
+   real(dp), intent(in) :: R1(3), R2(3)
+   real(dp), intent(out) :: diff(3)
+
+   integer :: i
+
+   diff= R2-R1
+   diff= diff-floor(diff)
+
+   do i=1, 3
+      if (diff(i)>0.5000000d0) diff(i)= diff(i)-1d0
+   enddo
+
+   return
+end subroutine periodic_diff
+
+!> cross product of two 3-value vectors
+!> R3=R1 x R2
+subroutine cross_product(R1, R2, R3)
+   use para, only : dp
+   implicit none
+
+   real(dp), intent(in) :: R1(3), R2(3)
+   real(dp), intent(out) :: R3(3)
+
+   R3(1)= R1(2)*R2(3)- R1(3)*R2(2)
+   R3(2)= R1(3)*R2(1)- R1(1)*R2(3)
+   R3(3)= R1(1)*R2(2)- R1(2)*R2(1)
+
+   return
+end subroutine cross_product
+
+
+      Module Kronecker
+
+      contains
+
+! Takes in Matrices A(i,j),B(k,l), assumed 2D, returns Kronecker Product
+! C(i*k,j*l)
+      function KronProd(A,B) result(C)
+
+       use para, only : Dp
+       IMPLICIT NONE
+
+       complex(Dp), dimension (:,:), intent(in)  :: A, B
+       complex(Dp), dimension (:,:), allocatable :: C
+       !real, dimension (:,:), intent(in)  :: A, B
+       !real, dimension (:,:), allocatable :: C
+       integer :: i = 0, j = 0, k = 0, l = 0
+       integer :: m = 0, n = 0, p = 0, q = 0
+
+
+       allocate(C(size(A,1)*size(B,1),size(A,2)*size(B,2)))
+       C = 0
+
+       do i = 1,size(A,1)
+        do j = 1,size(A,2)
+         n=(i-1)*size(B,1) + 1
+         m=n+size(B,1) - 1
+         p=(j-1)*size(B,2) + 1
+         q=p+size(B,2) - 1
+         C(n:m,p:q) = A(i,j)*B
+        enddo
+       enddo
+
+      end function KronProd
+      end module Kronecker
+